diff --git a/ts/audio/abstract_audio_renderer.ts b/ts/audio/abstract_audio_renderer.ts
index d03d9d5e3..14235f7a5 100644
--- a/ts/audio/abstract_audio_renderer.ts
+++ b/ts/audio/abstract_audio_renderer.ts
@@ -18,7 +18,7 @@
  * @author volker.sorge@gmail.com (Volker Sorge)
  */
 
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import { KeyCode } from '../common/event_util.js';
 import { AudioRenderer } from './audio_renderer.js';
 import { AuditoryDescription } from './auditory_description.js';
diff --git a/ts/audio/audio_util.ts b/ts/audio/audio_util.ts
index 05a44abb1..a0d260214 100644
--- a/ts/audio/audio_util.ts
+++ b/ts/audio/audio_util.ts
@@ -20,7 +20,7 @@
 
 import { setdifference } from '../common/base_util.js';
 import * as EngineConst from '../common/engine_const.js';
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import { AuditoryDescription } from './auditory_description.js';
 import { Span } from './span.js';
 
diff --git a/ts/audio/aural_rendering.ts b/ts/audio/aural_rendering.ts
index 14f2007cc..03455d934 100644
--- a/ts/audio/aural_rendering.ts
+++ b/ts/audio/aural_rendering.ts
@@ -19,7 +19,7 @@
  * @author volker.sorge@gmail.com (Volker Sorge)
  */
 
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import * as EngineConst from '../common/engine_const.js';
 import { AcssRenderer } from './acss_renderer.js';
 import { AudioRenderer } from './audio_renderer.js';
diff --git a/ts/audio/layout_renderer.ts b/ts/audio/layout_renderer.ts
index f07a08223..038735b38 100644
--- a/ts/audio/layout_renderer.ts
+++ b/ts/audio/layout_renderer.ts
@@ -21,7 +21,7 @@
 import { Debugger } from '../common/debugger.js';
 import * as DomUtil from '../common/dom_util.js';
 import * as EngineConst from '../common/engine_const.js';
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import * as AudioUtil from './audio_util.js';
 import { AuditoryDescription } from './auditory_description.js';
 import { XmlRenderer } from './xml_renderer.js';
diff --git a/ts/audio/ssml_renderer.ts b/ts/audio/ssml_renderer.ts
index 252f9ed21..8e27ab50a 100644
--- a/ts/audio/ssml_renderer.ts
+++ b/ts/audio/ssml_renderer.ts
@@ -18,7 +18,7 @@
  * @author volker.sorge@gmail.com (Volker Sorge)
  */
 
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import * as EngineConst from '../common/engine_const.js';
 import { Pause } from './audio_util.js';
 import { AuditoryDescription } from './auditory_description.js';
diff --git a/ts/audio/string_renderer.ts b/ts/audio/string_renderer.ts
index 66aa6e44c..2486854b2 100644
--- a/ts/audio/string_renderer.ts
+++ b/ts/audio/string_renderer.ts
@@ -18,7 +18,7 @@
  * @author volker.sorge@gmail.com (Volker Sorge)
  */
 
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import { AbstractAudioRenderer } from './abstract_audio_renderer.js';
 import { personalityMarkup } from './audio_util.js';
 import { AuditoryDescription } from './auditory_description.js';
diff --git a/ts/common/browser_util.ts b/ts/common/browser_util.ts
index 9778415d3..86093a8b0 100644
--- a/ts/common/browser_util.ts
+++ b/ts/common/browser_util.ts
@@ -18,7 +18,7 @@
  * @author volker.sorge@gmail.com (Volker Sorge)
  */
 
-import SystemExternal from './system_external.js';
+import { SystemExternal } from './system_external.js';
 import { xpath } from './xpath_util.js';
 
 /**
diff --git a/ts/common/cli.ts b/ts/common/cli.ts
index 9c2f3496a..71518e9da 100644
--- a/ts/common/cli.ts
+++ b/ts/common/cli.ts
@@ -27,7 +27,7 @@ import { EnginePromise, SREError } from './engine.js';
 import * as EngineConst from './engine_const.js';
 import * as ProcessorFactory from './processor_factory.js';
 import * as System from './system.js';
-import SystemExternal from './system_external.js';
+import { SystemExternal } from './system_external.js';
 import { Variables } from './variables.js';
 
 export class Cli {
diff --git a/ts/common/debugger.ts b/ts/common/debugger.ts
index ee0bbf5ad..1f7809e94 100644
--- a/ts/common/debugger.ts
+++ b/ts/common/debugger.ts
@@ -18,7 +18,7 @@
  * @author volker.sorge@gmail.com (Volker Sorge)
  */
 
-import SystemExternal from './system_external.js';
+import { SystemExternal } from './system_external.js';
 
 export class Debugger {
   private static instance: Debugger;
diff --git a/ts/common/dom_util.ts b/ts/common/dom_util.ts
index d8f1f0a73..b673312dd 100644
--- a/ts/common/dom_util.ts
+++ b/ts/common/dom_util.ts
@@ -22,9 +22,9 @@
  * @author volker.sorge@gmail.com (Volker Sorge)
  */
 
-import Engine, { SREError } from './engine.js';
+import { Engine, SREError } from './engine.js';
 import * as EngineConst from '../common/engine_const.js';
-import SystemExternal from './system_external.js';
+import { SystemExternal } from './system_external.js';
 import * as XpathUtil from './xpath_util.js';
 
 /**
diff --git a/ts/common/engine.ts b/ts/common/engine.ts
index 5c38cbc09..92a073b7c 100644
--- a/ts/common/engine.ts
+++ b/ts/common/engine.ts
@@ -51,7 +51,7 @@ export class SREError extends Error {
  * Initializes the basic Speech engine and contains some global context.
  *
  */
-export default class Engine {
+export class Engine {
   /**
    * Binary feature vector.
    */
diff --git a/ts/common/engine_setup.ts b/ts/common/engine_setup.ts
index 71cf14ed3..964936a6c 100644
--- a/ts/common/engine_setup.ts
+++ b/ts/common/engine_setup.ts
@@ -22,9 +22,9 @@ import * as L10n from '../l10n/l10n.js';
 import * as MathMap from '../speech_rules/math_map.js';
 import * as BrowserUtil from './browser_util.js';
 import { Debugger } from './debugger.js';
-import Engine, { EnginePromise } from './engine.js';
+import { Engine, EnginePromise } from './engine.js';
 import * as FileUtil from './file_util.js';
-import SystemExternal from './system_external.js';
+import { SystemExternal } from './system_external.js';
 
 // Engine setup method.
 /**
diff --git a/ts/common/file_util.ts b/ts/common/file_util.ts
index 245c506d4..8b393abdb 100644
--- a/ts/common/file_util.ts
+++ b/ts/common/file_util.ts
@@ -19,7 +19,7 @@
  * @author volker.sorge@gmail.com (Volker Sorge)
  */
 
-import SystemExternal from './system_external.js';
+import { SystemExternal } from './system_external.js';
 
 /**
  * Corrects pathnames to have trailing slashes.
diff --git a/ts/common/processor_factory.ts b/ts/common/processor_factory.ts
index ec1dcc1de..a70390951 100644
--- a/ts/common/processor_factory.ts
+++ b/ts/common/processor_factory.ts
@@ -28,7 +28,7 @@ import * as SpeechGeneratorUtil from '../speech_generator/speech_generator_util.
 import * as WalkerFactory from '../walker/walker_factory.js';
 import * as WalkerUtil from '../walker/walker_util.js';
 import * as DomUtil from './dom_util.js';
-import Engine, { SREError } from './engine.js';
+import { Engine, SREError } from './engine.js';
 import * as EngineConst from '../common/engine_const.js';
 import { KeyCode } from './event_util.js';
 import { Processor, KeyProcessor } from './processor.js';
diff --git a/ts/common/system.ts b/ts/common/system.ts
index 784e18f22..fb15f7398 100644
--- a/ts/common/system.ts
+++ b/ts/common/system.ts
@@ -20,13 +20,13 @@
 
 import { AuditoryDescription } from '../audio/auditory_description.js';
 
-import Engine, { EnginePromise, SREError } from './engine.js';
+import { Engine, EnginePromise, SREError } from './engine.js';
 import { setup } from './engine_setup.js';
 import * as EngineConst from './engine_const.js';
 import { KeyCode } from './event_util.js';
 import * as FileUtil from './file_util.js';
 import * as ProcessorFactory from './processor_factory.js';
-import SystemExternal from './system_external.js';
+import { SystemExternal } from './system_external.js';
 import { Variables } from './variables.js';
 import { standardLoader } from '../speech_rules/math_map.js';
 
diff --git a/ts/common/system_external.ts b/ts/common/system_external.ts
index ead342bf6..0712d61ed 100644
--- a/ts/common/system_external.ts
+++ b/ts/common/system_external.ts
@@ -27,7 +27,7 @@ declare let global: any;
 declare let require: (name: string) => any;
 declare let process: any;
 
-export default class SystemExternal {
+export class SystemExternal {
   /**
    * The local require function for NodeJS.
    *
diff --git a/ts/common/xpath_util.ts b/ts/common/xpath_util.ts
index 56f1e79ff..48e7f1358 100644
--- a/ts/common/xpath_util.ts
+++ b/ts/common/xpath_util.ts
@@ -22,9 +22,9 @@
  * @author volker.sorge@gmail.com (Volker Sorge)
  */
 
-import Engine from './engine.js';
+import { Engine } from './engine.js';
 import * as EngineConst from '../common/engine_const.js';
-import SystemExternal from './system_external.js';
+import { SystemExternal } from './system_external.js';
 
 /**
  * Returns whether or not xpath is supported.
diff --git a/ts/enrich_mathml/enrich_mathml.ts b/ts/enrich_mathml/enrich_mathml.ts
index e89b4cd26..7dbad57da 100644
--- a/ts/enrich_mathml/enrich_mathml.ts
+++ b/ts/enrich_mathml/enrich_mathml.ts
@@ -23,7 +23,7 @@
 
 import { Debugger } from '../common/debugger.js';
 import * as DomUtil from '../common/dom_util.js';
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import { NamedSymbol } from '../semantic_tree/semantic_attr.js';
 import {
   SemanticRole,
diff --git a/ts/l10n/l10n.ts b/ts/l10n/l10n.ts
index 9a0c80be4..0fa3420da 100644
--- a/ts/l10n/l10n.ts
+++ b/ts/l10n/l10n.ts
@@ -18,7 +18,7 @@
  * @author volker.sorge@gmail.com (Volker Sorge)
  */
 
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import { Variables } from '../common/variables.js';
 import { Grammar } from '../rule_engine/grammar.js';
 
diff --git a/ts/l10n/locales/locale_af.ts b/ts/l10n/locales/locale_af.ts
index 2b12e50a0..16a07e77a 100644
--- a/ts/l10n/locales/locale_af.ts
+++ b/ts/l10n/locales/locale_af.ts
@@ -21,7 +21,7 @@
 import { Grammar } from '../../rule_engine/grammar.js';
 import { nestingToString } from '../locale_util.js';
 import { createLocale, Locale } from '../locale.js';
-import NUMBERS from '../numbers/numbers_af.js';
+import { NUMBERS } from '../numbers/numbers_af.js';
 import * as tr from '../transformers.js';
 
 const germanPostfixCombiner = function (
diff --git a/ts/l10n/locales/locale_ca.ts b/ts/l10n/locales/locale_ca.ts
index 0e9d1a9dc..22c3e3188 100644
--- a/ts/l10n/locales/locale_ca.ts
+++ b/ts/l10n/locales/locale_ca.ts
@@ -24,7 +24,7 @@
 
 import { createLocale, Locale } from '../locale.js';
 import { combinePostfixIndex } from '../locale_util.js';
-import NUMBERS from '../numbers/numbers_ca.js';
+import { NUMBERS } from '../numbers/numbers_ca.js';
 import { Combiners } from '../transformers.js';
 
 const sansserifCombiner = function (letter: string, font: string, cap: string) {
diff --git a/ts/l10n/locales/locale_da.ts b/ts/l10n/locales/locale_da.ts
index f900fc620..7668d0bec 100644
--- a/ts/l10n/locales/locale_da.ts
+++ b/ts/l10n/locales/locale_da.ts
@@ -20,7 +20,7 @@
 
 import { createLocale, Locale } from '../locale.js';
 import { nestingToString } from '../locale_util.js';
-import NUMBERS from '../numbers/numbers_da.js';
+import { NUMBERS } from '../numbers/numbers_da.js';
 import * as tr from '../transformers.js';
 
 let locale: Locale = null;
diff --git a/ts/l10n/locales/locale_de.ts b/ts/l10n/locales/locale_de.ts
index 3c9a1e4d2..166418a6e 100644
--- a/ts/l10n/locales/locale_de.ts
+++ b/ts/l10n/locales/locale_de.ts
@@ -25,7 +25,7 @@
 import { Grammar } from '../../rule_engine/grammar.js';
 import { localFont } from '../locale_util.js';
 import { createLocale, Locale } from '../locale.js';
-import NUMBERS from '../numbers/numbers_de.js';
+import { NUMBERS } from '../numbers/numbers_de.js';
 
 const germanPrefixCombiner = function (
   letter: string,
diff --git a/ts/l10n/locales/locale_en.ts b/ts/l10n/locales/locale_en.ts
index 209b0e0ab..2679ae4fc 100644
--- a/ts/l10n/locales/locale_en.ts
+++ b/ts/l10n/locales/locale_en.ts
@@ -21,7 +21,7 @@
 import { Grammar } from '../../rule_engine/grammar.js';
 import { createLocale, Locale } from '../locale.js';
 import { nestingToString } from '../locale_util.js';
-import NUMBERS from '../numbers/numbers_en.js';
+import { NUMBERS } from '../numbers/numbers_en.js';
 import * as tr from '../transformers.js';
 
 let locale: Locale = null;
diff --git a/ts/l10n/locales/locale_es.ts b/ts/l10n/locales/locale_es.ts
index 1f567a7ae..03f3aa111 100644
--- a/ts/l10n/locales/locale_es.ts
+++ b/ts/l10n/locales/locale_es.ts
@@ -24,7 +24,7 @@
 
 import { createLocale, Locale } from '../locale.js';
 import { combinePostfixIndex } from '../locale_util.js';
-import NUMBERS from '../numbers/numbers_es.js';
+import { NUMBERS } from '../numbers/numbers_es.js';
 import { Combiners } from '../transformers.js';
 
 const sansserifCombiner = function (letter: string, font: string, cap: string) {
diff --git a/ts/l10n/locales/locale_fr.ts b/ts/l10n/locales/locale_fr.ts
index 426e755ed..3f16f08f3 100644
--- a/ts/l10n/locales/locale_fr.ts
+++ b/ts/l10n/locales/locale_fr.ts
@@ -25,7 +25,7 @@
 import { Grammar } from '../../rule_engine/grammar.js';
 import { createLocale, Locale } from '../locale.js';
 import { combinePostfixIndex, nestingToString } from '../locale_util.js';
-import NUMBERS from '../numbers/numbers_fr.js';
+import { NUMBERS } from '../numbers/numbers_fr.js';
 import { Combiners } from '../transformers.js';
 
 let locale: Locale = null;
diff --git a/ts/l10n/locales/locale_hi.ts b/ts/l10n/locales/locale_hi.ts
index 519f68e06..beaee2f0d 100644
--- a/ts/l10n/locales/locale_hi.ts
+++ b/ts/l10n/locales/locale_hi.ts
@@ -23,7 +23,7 @@
 //
 
 import { createLocale, Locale } from '../locale.js';
-import NUMBERS from '../numbers/numbers_hi.js';
+import { NUMBERS } from '../numbers/numbers_hi.js';
 import { Combiners } from '../transformers.js';
 import { nestingToString } from '../locale_util.js';
 
diff --git a/ts/l10n/locales/locale_it.ts b/ts/l10n/locales/locale_it.ts
index 5546a27ff..38f1327e6 100644
--- a/ts/l10n/locales/locale_it.ts
+++ b/ts/l10n/locales/locale_it.ts
@@ -24,7 +24,7 @@
 
 import { combinePostfixIndex, nestingToString } from '../locale_util.js';
 import { createLocale, Locale } from '../locale.js';
-import NUMBERS from '../numbers/numbers_it.js';
+import { NUMBERS } from '../numbers/numbers_it.js';
 import { Combiners } from '../transformers.js';
 
 const italianPostfixCombiner = function (
diff --git a/ts/l10n/locales/locale_ko.ts b/ts/l10n/locales/locale_ko.ts
index 6b2ba84f4..c48b4b544 100644
--- a/ts/l10n/locales/locale_ko.ts
+++ b/ts/l10n/locales/locale_ko.ts
@@ -22,7 +22,7 @@
 import { Grammar } from '../../rule_engine/grammar.js';
 import { createLocale, Locale } from '../locale.js';
 import { nestingToString } from '../locale_util.js';
-import NUMBERS from '../numbers/numbers_ko.js';
+import { NUMBERS } from '../numbers/numbers_ko.js';
 import * as tr from '../transformers.js';
 
 
diff --git a/ts/l10n/locales/locale_nb.ts b/ts/l10n/locales/locale_nb.ts
index 0cedf0730..0b846160e 100644
--- a/ts/l10n/locales/locale_nb.ts
+++ b/ts/l10n/locales/locale_nb.ts
@@ -24,7 +24,7 @@
 
 import { createLocale, Locale } from '../locale.js';
 import { nestingToString } from '../locale_util.js';
-import NUMBERS from '../numbers/numbers_nn.js';
+import { NUMBERS } from '../numbers/numbers_nn.js';
 import * as tr from '../transformers.js';
 
 let locale: Locale = null;
diff --git a/ts/l10n/locales/locale_nemeth.ts b/ts/l10n/locales/locale_nemeth.ts
index 3e148e215..f8e068851 100644
--- a/ts/l10n/locales/locale_nemeth.ts
+++ b/ts/l10n/locales/locale_nemeth.ts
@@ -24,7 +24,7 @@
 //
 
 import { createLocale, Locale } from '../locale.js';
-import NUMBERS from '../numbers/numbers_nemeth.js';
+import { NUMBERS } from '../numbers/numbers_nemeth.js';
 import { identityTransformer } from '../transformers.js';
 
 /**
diff --git a/ts/l10n/locales/locale_nn.ts b/ts/l10n/locales/locale_nn.ts
index e15a67ed1..27c5b7cac 100644
--- a/ts/l10n/locales/locale_nn.ts
+++ b/ts/l10n/locales/locale_nn.ts
@@ -24,7 +24,7 @@
 
 import { createLocale, Locale } from '../locale.js';
 import { nestingToString } from '../locale_util.js';
-import NUMBERS from '../numbers/numbers_nn.js';
+import { NUMBERS } from '../numbers/numbers_nn.js';
 import * as tr from '../transformers.js';
 
 let locale: Locale = null;
diff --git a/ts/l10n/locales/locale_sv.ts b/ts/l10n/locales/locale_sv.ts
index 268922026..6a5128a42 100644
--- a/ts/l10n/locales/locale_sv.ts
+++ b/ts/l10n/locales/locale_sv.ts
@@ -20,7 +20,7 @@
 
 import { createLocale, Locale } from '../locale.js';
 import { nestingToString } from '../locale_util.js';
-import NUMBERS from '../numbers/numbers_sv.js';
+import { NUMBERS } from '../numbers/numbers_sv.js';
 import * as tr from '../transformers.js';
 
 let locale: Locale = null;
diff --git a/ts/l10n/messages.ts b/ts/l10n/messages.ts
index 0d1db85a2..2f4107441 100644
--- a/ts/l10n/messages.ts
+++ b/ts/l10n/messages.ts
@@ -85,33 +85,36 @@ export interface Numbers {
   special?: { [key: string]: string | string[] };
 
   // Constructor methods
-  wordOrdinal: tr.Transformer;
-  numericOrdinal: tr.Transformer;
-  numberToWords: tr.Transformer;
-  numberToOrdinal: tr.GrammarCase;
+  wordOrdinal?: tr.Transformer;
+  numericOrdinal?: tr.Transformer;
+  numberToWords?: tr.Transformer;
+  numberToOrdinal?: tr.GrammarCase;
 
-  vulgarSep: string;
-  numSep: string;
+  vulgarSep?: string;
+  numSep?: string;
 }
 
 /**
  * @returns A numbers structure.
  */
-export function NUMBERS(): Numbers {
-  return {
-    zero: 'zero',
-    ones: [],
-    tens: [],
-    large: [],
-    special: {},
+export function NUMBERS(numbers: Numbers = {}): Numbers {
+  return Object.assign(
+    {
+      zero: 'zero',
+      ones: [],
+      tens: [],
+      large: [],
+      special: {},
 
-    wordOrdinal: tr.identityTransformer,
-    numericOrdinal: tr.identityTransformer,
-    numberToWords: tr.identityTransformer,
-    numberToOrdinal: tr.pluralCase,
-    vulgarSep: ' ',
-    numSep: ' '
-  };
+      wordOrdinal: tr.identityTransformer,
+      numericOrdinal: tr.identityTransformer,
+      numberToWords: tr.identityTransformer,
+      numberToOrdinal: tr.pluralCase,
+      vulgarSep: ' ',
+      numSep: ' '
+    },
+    numbers
+  );
 }
 
 /**
diff --git a/ts/l10n/numbers/numbers_af.ts b/ts/l10n/numbers/numbers_af.ts
index 2b686d7cd..fc0caa7ed 100644
--- a/ts/l10n/numbers/numbers_af.ts
+++ b/ts/l10n/numbers/numbers_af.ts
@@ -132,10 +132,11 @@ function numericOrdinal(num: number): string {
   return num.toString() + '.';
 }
 
-const NUMBERS: Numbers = NUMB();
-NUMBERS.wordOrdinal = wordOrdinal;
-NUMBERS.numericOrdinal = numericOrdinal;
-NUMBERS.numberToWords = numberToWords;
-NUMBERS.numberToOrdinal = numberToOrdinal;
-
-export default NUMBERS;
+export const NUMBERS: Numbers = NUMB(
+  {
+    'wordOrdinal': wordOrdinal,
+    'numericOrdinal': numericOrdinal,
+    'numberToWords': numberToWords,
+    'numberToOrdinal': numberToOrdinal,
+  }
+);
diff --git a/ts/l10n/numbers/numbers_ca.ts b/ts/l10n/numbers/numbers_ca.ts
index fd784a57a..00195e6a4 100644
--- a/ts/l10n/numbers/numbers_ca.ts
+++ b/ts/l10n/numbers/numbers_ca.ts
@@ -144,9 +144,10 @@ function numericOrdinal(num: number): string {
   return num.toString() + (gender === 'f' ? 'a' : 'n');
 }
 
-const NUMBERS: Numbers = NUMB();
-NUMBERS.numericOrdinal = numericOrdinal;
-NUMBERS.numberToWords = numberToWords;
-NUMBERS.numberToOrdinal = numberToOrdinal;
-
-export default NUMBERS;
+export const NUMBERS: Numbers = NUMB(
+  {
+    'numericOrdinal': numericOrdinal,
+    'numberToWords': numberToWords,
+    'numberToOrdinal': numberToOrdinal,
+  }
+);
diff --git a/ts/l10n/numbers/numbers_da.ts b/ts/l10n/numbers/numbers_da.ts
index 04c6fb460..278ffd1e0 100644
--- a/ts/l10n/numbers/numbers_da.ts
+++ b/ts/l10n/numbers/numbers_da.ts
@@ -146,10 +146,11 @@ function numericOrdinal(num: number): string {
   return num.toString() + '.';
 }
 
-const NUMBERS: Numbers = NUMB();
-NUMBERS.wordOrdinal = wordOrdinal;
-NUMBERS.numericOrdinal = numericOrdinal;
-NUMBERS.numberToWords = numberToWords;
-NUMBERS.numberToOrdinal = numberToOrdinal;
-
-export default NUMBERS;
+export const NUMBERS: Numbers = NUMB(
+  {
+    'wordOrdinal': wordOrdinal,
+    'numericOrdinal': numericOrdinal,
+    'numberToWords': numberToWords,
+    'numberToOrdinal': numberToOrdinal,
+  }
+);
diff --git a/ts/l10n/numbers/numbers_de.ts b/ts/l10n/numbers/numbers_de.ts
index acfe5a489..a0befc5bb 100644
--- a/ts/l10n/numbers/numbers_de.ts
+++ b/ts/l10n/numbers/numbers_de.ts
@@ -146,10 +146,11 @@ function numericOrdinal(num: number): string {
   return num.toString() + '.';
 }
 
-const NUMBERS: Numbers = NUMB();
-NUMBERS.wordOrdinal = wordOrdinal;
-NUMBERS.numericOrdinal = numericOrdinal;
-NUMBERS.numberToWords = numberToWords;
-NUMBERS.numberToOrdinal = numberToOrdinal;
-
-export default NUMBERS;
+export const NUMBERS: Numbers = NUMB(
+  {
+    'wordOrdinal': wordOrdinal,
+    'numericOrdinal': numericOrdinal,
+    'numberToWords': numberToWords,
+    'numberToOrdinal': numberToOrdinal,
+  }
+);
diff --git a/ts/l10n/numbers/numbers_en.ts b/ts/l10n/numbers/numbers_en.ts
index bb1133366..d615eb208 100644
--- a/ts/l10n/numbers/numbers_en.ts
+++ b/ts/l10n/numbers/numbers_en.ts
@@ -145,11 +145,11 @@ function numericOrdinal(num: number): string {
   }
 }
 
-const NUMBERS: Numbers = NUMB();
-NUMBERS.wordOrdinal = wordOrdinal;
-NUMBERS.numericOrdinal = numericOrdinal;
-NUMBERS.numberToWords = numberToWords;
-NUMBERS.numberToOrdinal = numberToOrdinal;
-
-export default NUMBERS;
-// TODO: For simple speech output this should be different.
+export const NUMBERS: Numbers = NUMB(
+  {
+    'wordOrdinal': wordOrdinal,
+    'numericOrdinal': numericOrdinal,
+    'numberToWords': numberToWords,
+    'numberToOrdinal': numberToOrdinal,
+  }
+);
diff --git a/ts/l10n/numbers/numbers_es.ts b/ts/l10n/numbers/numbers_es.ts
index df887186f..491891f9b 100644
--- a/ts/l10n/numbers/numbers_es.ts
+++ b/ts/l10n/numbers/numbers_es.ts
@@ -152,9 +152,10 @@ function numericOrdinal(num: number): string {
   return num.toString() + (gender === 'f' ? 'a' : 'o');
 }
 
-const NUMBERS: Numbers = NUMB();
-NUMBERS.numericOrdinal = numericOrdinal;
-NUMBERS.numberToWords = numberToWords;
-NUMBERS.numberToOrdinal = numberToOrdinal;
-
-export default NUMBERS;
+export const NUMBERS: Numbers = NUMB(
+  {
+    'numericOrdinal': numericOrdinal,
+    'numberToWords': numberToWords,
+    'numberToOrdinal': numberToOrdinal,
+  }
+);
diff --git a/ts/l10n/numbers/numbers_fr.ts b/ts/l10n/numbers/numbers_fr.ts
index 30aa33c0e..5b8ecb76e 100644
--- a/ts/l10n/numbers/numbers_fr.ts
+++ b/ts/l10n/numbers/numbers_fr.ts
@@ -22,7 +22,7 @@
 // This work was sponsored by TextHelp
 //
 
-import Engine from '../../common/engine.js';
+import { Engine } from '../../common/engine.js';
 import { Grammar } from '../../rule_engine/grammar.js';
 import { Numbers, NUMBERS as NUMB } from '../messages.js';
 
@@ -167,10 +167,11 @@ function numericOrdinal(num: number): string {
     : num.toString() + 'e';
 }
 
-const NUMBERS: Numbers = NUMB();
-NUMBERS.wordOrdinal = wordOrdinal;
-NUMBERS.numericOrdinal = numericOrdinal;
-NUMBERS.numberToWords = numberToWords;
-NUMBERS.numberToOrdinal = numberToOrdinal;
-
-export default NUMBERS;
+export const NUMBERS: Numbers = NUMB(
+  {
+    'wordOrdinal': wordOrdinal,
+    'numericOrdinal': numericOrdinal,
+    'numberToWords': numberToWords,
+    'numberToOrdinal': numberToOrdinal,
+  }
+);
diff --git a/ts/l10n/numbers/numbers_hi.ts b/ts/l10n/numbers/numbers_hi.ts
index de9b19257..57185f2d9 100644
--- a/ts/l10n/numbers/numbers_hi.ts
+++ b/ts/l10n/numbers/numbers_hi.ts
@@ -143,10 +143,11 @@ function numericOrdinal(num: number): string {
   return ordinal + (gender === 'f' ? 'वीं' : 'वाँ');
 }
 
-const NUMBERS: Numbers = NUMB();
-NUMBERS.wordOrdinal = wordOrdinal;
-NUMBERS.numericOrdinal = numericOrdinal;
-NUMBERS.numberToWords = numberToWords;
-NUMBERS.numberToOrdinal = numberToOrdinal;
-
-export default NUMBERS;
+export const NUMBERS: Numbers = NUMB(
+  {
+    'wordOrdinal': wordOrdinal,
+    'numericOrdinal': numericOrdinal,
+    'numberToWords': numberToWords,
+    'numberToOrdinal': numberToOrdinal,
+  }
+);
diff --git a/ts/l10n/numbers/numbers_it.ts b/ts/l10n/numbers/numbers_it.ts
index 4c9a890e8..46f324547 100644
--- a/ts/l10n/numbers/numbers_it.ts
+++ b/ts/l10n/numbers/numbers_it.ts
@@ -136,10 +136,11 @@ function numericOrdinal(num: number): string {
   return num.toString() + (gender === 'm' ? 'o' : 'a');
 }
 
-const NUMBERS: Numbers = NUMB();
-NUMBERS.wordOrdinal = wordOrdinal;
-NUMBERS.numericOrdinal = numericOrdinal;
-NUMBERS.numberToWords = numberToWords;
-NUMBERS.numberToOrdinal = numberToOrdinal;
-
-export default NUMBERS;
+export const NUMBERS: Numbers = NUMB(
+  {
+    'wordOrdinal': wordOrdinal,
+    'numericOrdinal': numericOrdinal,
+    'numberToWords': numberToWords,
+    'numberToOrdinal': numberToOrdinal,
+  }
+);
diff --git a/ts/l10n/numbers/numbers_ko.ts b/ts/l10n/numbers/numbers_ko.ts
index 413b786ea..fb7fe4f8f 100644
--- a/ts/l10n/numbers/numbers_ko.ts
+++ b/ts/l10n/numbers/numbers_ko.ts
@@ -104,10 +104,11 @@ function numericOrdinal(num: number): string {
   return numberToOrdinal(num, false);
 }
 
-const NUMBERS: Numbers = NUMB();
-NUMBERS.wordOrdinal = wordOrdinal;
-NUMBERS.numericOrdinal = numericOrdinal;
-NUMBERS.numberToWords = numberToWords;
-NUMBERS.numberToOrdinal = numberToOrdinal;
-
-export default NUMBERS;
+export const NUMBERS: Numbers = NUMB(
+  {
+    'wordOrdinal': wordOrdinal,
+    'numericOrdinal': numericOrdinal,
+    'numberToWords': numberToWords,
+    'numberToOrdinal': numberToOrdinal,
+  }
+);
diff --git a/ts/l10n/numbers/numbers_nemeth.ts b/ts/l10n/numbers/numbers_nemeth.ts
index 797da7719..d67804364 100644
--- a/ts/l10n/numbers/numbers_nemeth.ts
+++ b/ts/l10n/numbers/numbers_nemeth.ts
@@ -39,8 +39,9 @@ function numberToWords(num: number): string {
     .join('');
 }
 
-const NUMBERS: Numbers = NUMB();
-NUMBERS.numberToWords = numberToWords;
-NUMBERS.numberToOrdinal = numberToWords;
-
-export default NUMBERS;
+export const NUMBERS: Numbers = NUMB(
+  {
+    'numberToWords': numberToWords,
+    'numberToOrdinal': numberToWords,
+  }
+);
diff --git a/ts/l10n/numbers/numbers_nn.ts b/ts/l10n/numbers/numbers_nn.ts
index efa28becc..891c9c4ee 100644
--- a/ts/l10n/numbers/numbers_nn.ts
+++ b/ts/l10n/numbers/numbers_nn.ts
@@ -18,7 +18,7 @@
  * @author volker.sorge@gmail.com (Volker Sorge)
  */
 
-import Engine from '../../common/engine.js';
+import { Engine } from '../../common/engine.js';
 import { Numbers, NUMBERS as NUMB } from '../messages.js';
 
 /**
@@ -154,13 +154,14 @@ function numericOrdinal(num: number): string {
   return num.toString() + '.';
 }
 
-const NUMBERS: Numbers = NUMB();
-NUMBERS.wordOrdinal = wordOrdinal;
-NUMBERS.numericOrdinal = numericOrdinal;
-NUMBERS.numberToWords = numberToWords;
-NUMBERS.numberToOrdinal = numberToOrdinal;
-
-export default NUMBERS;
+export const NUMBERS: Numbers = NUMB(
+  {
+    'wordOrdinal': wordOrdinal,
+    'numericOrdinal': numericOrdinal,
+    'numberToWords': numberToWords,
+    'numberToOrdinal': numberToOrdinal,
+  }
+);
 // TODO: For simple speech output this should be different.
 
 // Alternative Germanic style numbers:
diff --git a/ts/l10n/numbers/numbers_sv.ts b/ts/l10n/numbers/numbers_sv.ts
index 7616f9676..c19282b14 100644
--- a/ts/l10n/numbers/numbers_sv.ts
+++ b/ts/l10n/numbers/numbers_sv.ts
@@ -161,11 +161,11 @@ function numericOrdinal(num: number): string {
   return str + (str.match(/1$|2$/) ? ':a' : ':e');
 }
 
-const NUMBERS: Numbers = NUMB();
-NUMBERS.wordOrdinal = wordOrdinal;
-NUMBERS.numericOrdinal = numericOrdinal;
-NUMBERS.numberToWords = numberToWords;
-NUMBERS.numberToOrdinal = numberToOrdinal;
-
-export default NUMBERS;
-// TODO: For simple speech output this should be different.
+export const NUMBERS: Numbers = NUMB(
+  {
+    'wordOrdinal': wordOrdinal,
+    'numericOrdinal': numericOrdinal,
+    'numberToWords': numberToWords,
+    'numberToOrdinal': numberToOrdinal,
+  }
+);
diff --git a/ts/rule_engine/grammar.ts b/ts/rule_engine/grammar.ts
index 03da9e347..c30c6672a 100644
--- a/ts/rule_engine/grammar.ts
+++ b/ts/rule_engine/grammar.ts
@@ -23,7 +23,7 @@
  */
 
 import * as DomUtil from '../common/dom_util.js';
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import * as LocaleUtil from '../l10n/locale_util.js';
 import { LOCALE } from '../l10n/locale.js';
 import { DynamicCstr } from './dynamic_cstr.js';
diff --git a/ts/rule_engine/math_compound_store.ts b/ts/rule_engine/math_compound_store.ts
index 5b87a57b1..a9ec489b1 100644
--- a/ts/rule_engine/math_compound_store.ts
+++ b/ts/rule_engine/math_compound_store.ts
@@ -21,7 +21,7 @@
  * @author volker.sorge@gmail.com (Volker Sorge)
  */
 
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import { locales } from '../l10n/l10n.js';
 import { addFunctionSemantic } from '../semantic_tree/semantic_attr.js';
 import {
diff --git a/ts/rule_engine/math_simple_store.ts b/ts/rule_engine/math_simple_store.ts
index b8bbb9b64..f2a799591 100644
--- a/ts/rule_engine/math_simple_store.ts
+++ b/ts/rule_engine/math_simple_store.ts
@@ -24,7 +24,7 @@
  * @author sorge@google.com (Volker Sorge)
  */
 
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import { Axis, DynamicCstr } from './dynamic_cstr.js';
 
 export interface MappingsJson {
diff --git a/ts/rule_engine/speech_rule_engine.ts b/ts/rule_engine/speech_rule_engine.ts
index 0ca279e52..72944a8f2 100644
--- a/ts/rule_engine/speech_rule_engine.ts
+++ b/ts/rule_engine/speech_rule_engine.ts
@@ -33,7 +33,7 @@ import { AuditoryDescription, AuditoryList } from '../audio/auditory_description
 import { Span } from '../audio/span.js';
 import { Debugger } from '../common/debugger.js';
 import * as DomUtil from '../common/dom_util.js';
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import * as EngineConst from '../common/engine_const.js';
 import { evalXPath, updateEvaluator } from '../common/xpath_util.js';
 import { ClearspeakPreferences } from '../speech_rules/clearspeak_preferences.js';
diff --git a/ts/rule_engine/store_util.ts b/ts/rule_engine/store_util.ts
index ae55af520..c0b20f5c6 100644
--- a/ts/rule_engine/store_util.ts
+++ b/ts/rule_engine/store_util.ts
@@ -20,7 +20,7 @@
  */
 import { AuditoryDescription } from '../audio/auditory_description.js';
 import * as XpathUtil from '../common/xpath_util.js';
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 
 /**
  * Count list of nodes and concatenate this with the context string.
diff --git a/ts/semantic_tree/semantic_heuristics.ts b/ts/semantic_tree/semantic_heuristics.ts
index 617acb596..d7460b7c4 100644
--- a/ts/semantic_tree/semantic_heuristics.ts
+++ b/ts/semantic_tree/semantic_heuristics.ts
@@ -21,7 +21,7 @@
  */
 
 import { Debugger } from '../common/debugger.js';
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import { NamedSymbol } from './semantic_attr.js';
 import { SemanticHeuristics } from './semantic_heuristic_factory.js';
 import {
@@ -31,7 +31,7 @@ import {
 import { SemanticRole, SemanticType } from './semantic_meaning.js';
 import { SemanticNode } from './semantic_node.js';
 import * as SemanticPred from './semantic_pred.js';
-import SemanticProcessor from './semantic_processor.js';
+import { SemanticProcessor } from './semantic_processor.js';
 import * as SemanticUtil from './semantic_util.js';
 import { SemanticSkeleton } from './semantic_skeleton.js';
 import { MMLTAGS } from '../semantic_tree/semantic_util.js';
diff --git a/ts/semantic_tree/semantic_mathml.ts b/ts/semantic_tree/semantic_mathml.ts
index 053718362..458207b31 100644
--- a/ts/semantic_tree/semantic_mathml.ts
+++ b/ts/semantic_tree/semantic_mathml.ts
@@ -28,7 +28,7 @@ import { SemanticMap } from './semantic_attr.js';
 import { SemanticNode } from './semantic_node.js';
 import { SemanticAbstractParser } from './semantic_parser.js';
 import * as SemanticPred from './semantic_pred.js';
-import SemanticProcessor from './semantic_processor.js';
+import { SemanticProcessor } from './semantic_processor.js';
 import * as SemanticUtil from './semantic_util.js';
 import { MMLTAGS } from '../semantic_tree/semantic_util.js';
 
diff --git a/ts/semantic_tree/semantic_processor.ts b/ts/semantic_tree/semantic_processor.ts
index 2f489324d..b2d38d428 100644
--- a/ts/semantic_tree/semantic_processor.ts
+++ b/ts/semantic_tree/semantic_processor.ts
@@ -43,7 +43,7 @@ interface BoundsType {
   accent?: boolean;
 }
 
-export default class SemanticProcessor {
+export class SemanticProcessor {
   private static readonly FENCE_TO_PUNCT_: { [key: string]: SemanticRole } = {
     [SemanticRole.METRIC]: SemanticRole.METRIC,
     [SemanticRole.NEUTRAL]: SemanticRole.VBAR,
diff --git a/ts/semantic_tree/semantic_skeleton.ts b/ts/semantic_tree/semantic_skeleton.ts
index 7fd6772cd..7b9639180 100644
--- a/ts/semantic_tree/semantic_skeleton.ts
+++ b/ts/semantic_tree/semantic_skeleton.ts
@@ -20,7 +20,7 @@
  */
 
 import * as BaseUtil from '../common/base_util.js';
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 
 import * as XpathUtil from '../common/xpath_util.js';
 import { Attribute as EnrichAttribute } from '../enrich_mathml/enrich_attr.js';
diff --git a/ts/speech_rules/alphabet_generator.ts b/ts/speech_rules/alphabet_generator.ts
index 12fcc6af5..62dc45929 100644
--- a/ts/speech_rules/alphabet_generator.ts
+++ b/ts/speech_rules/alphabet_generator.ts
@@ -19,7 +19,7 @@
  */
 
 import * as Alphabet from './alphabet.js';
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import * as L10n from '../l10n/l10n.js';
 import { LOCALE } from '../l10n/locale.js';
 import { localeFontCombiner } from '../l10n/locale_util.js';
diff --git a/ts/speech_rules/clearspeak_preferences.ts b/ts/speech_rules/clearspeak_preferences.ts
index ebbec9d18..56c7b8dcd 100644
--- a/ts/speech_rules/clearspeak_preferences.ts
+++ b/ts/speech_rules/clearspeak_preferences.ts
@@ -18,7 +18,7 @@
  * @author volker.sorge@gmail.com (Volker Sorge)
  */
 
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import * as EngineConst from '../common/engine_const.js';
 import { DynamicCstr } from '../rule_engine/dynamic_cstr.js';
 import {
diff --git a/ts/speech_rules/clearspeak_util.ts b/ts/speech_rules/clearspeak_util.ts
index d3b9ea4ba..bb732f620 100644
--- a/ts/speech_rules/clearspeak_util.ts
+++ b/ts/speech_rules/clearspeak_util.ts
@@ -20,7 +20,7 @@
 
 import { Span } from '../audio/span.js';
 import * as DomUtil from '../common/dom_util.js';
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import * as XpathUtil from '../common/xpath_util.js';
 import { LOCALE } from '../l10n/locale.js';
 import { vulgarFractionSmall } from '../l10n/transformers.js';
diff --git a/ts/speech_rules/math_map.ts b/ts/speech_rules/math_map.ts
index 9f715b668..d02311ffd 100644
--- a/ts/speech_rules/math_map.ts
+++ b/ts/speech_rules/math_map.ts
@@ -22,10 +22,10 @@
  */
 
 import * as BrowserUtil from '../common/browser_util.js';
-import Engine, { EnginePromise } from '../common/engine.js';
+import { Engine, EnginePromise } from '../common/engine.js';
 import * as EngineConst from '../common/engine_const.js';
 import * as FileUtil from '../common/file_util.js';
-import SystemExternal from '../common/system_external.js';
+import { SystemExternal } from '../common/system_external.js';
 import { RulesJson } from '../rule_engine/base_rule_store.js';
 import { DynamicCstr } from '../rule_engine/dynamic_cstr.js';
 import * as MathCompoundStore from '../rule_engine/math_compound_store.js';
diff --git a/ts/speech_rules/mathspeak_util.ts b/ts/speech_rules/mathspeak_util.ts
index 9f17ca67e..ac3531a5e 100644
--- a/ts/speech_rules/mathspeak_util.ts
+++ b/ts/speech_rules/mathspeak_util.ts
@@ -32,7 +32,7 @@ import {
   SemanticType
 } from '../semantic_tree/semantic_meaning.js';
 import { SemanticNode } from '../semantic_tree/semantic_node.js';
-import SemanticProcessor from '../semantic_tree/semantic_processor.js';
+import { SemanticProcessor } from '../semantic_tree/semantic_processor.js';
 
 // import * as NumbersUtil from './numbers_util.js';
 
diff --git a/ts/speech_rules/nemeth_util.ts b/ts/speech_rules/nemeth_util.ts
index 291298755..adb25db3e 100644
--- a/ts/speech_rules/nemeth_util.ts
+++ b/ts/speech_rules/nemeth_util.ts
@@ -23,7 +23,7 @@ import { Span } from '../audio/span.js';
 import * as DomUtil from '../common/dom_util.js';
 import * as XpathUtil from '../common/xpath_util.js';
 import { Grammar, correctFont } from '../rule_engine/grammar.js';
-import Engine from '../common/engine.js';
+import { Engine } from '../common/engine.js';
 import { register, activate } from '../semantic_tree/semantic_annotations.js';
 import { SemanticVisitor } from '../semantic_tree/semantic_annotator.js';
 import {
diff --git a/ts/walker/rebuild_stree.ts b/ts/walker/rebuild_stree.ts
index a27824fda..1c11ff775 100644
--- a/ts/walker/rebuild_stree.ts
+++ b/ts/walker/rebuild_stree.ts
@@ -29,7 +29,7 @@ import {
 } from '../semantic_tree/semantic_meaning.js';
 import { SemanticNode } from '../semantic_tree/semantic_node.js';
 import { SemanticNodeFactory } from '../semantic_tree/semantic_node_factory.js';
-import SemanticProcessor from '../semantic_tree/semantic_processor.js';
+// import SemanticProcessor from '../semantic_tree/semantic_processor.js';
 import { SemanticSkeleton, Sexp } from '../semantic_tree/semantic_skeleton.js';
 import { SemanticTree } from '../semantic_tree/semantic_tree.js';
 import * as WalkerUtil from './walker_util.js';
@@ -115,7 +115,7 @@ export class RebuildStree {
     this.streeRoot = this.assembleTree(this.mmlRoot);
     this.stree = SemanticTree.fromNode(this.streeRoot, this.mathml);
     this.xml = this.stree.xml();
-    SemanticProcessor.getInstance().setNodeFactory(this.factory);
+    // SemanticProcessor.getInstance().setNodeFactory(this.factory);
   }
 
   /**