diff --git a/src/Analyser.php b/src/Analyser.php
index fa024de..1f5b549 100644
--- a/src/Analyser.php
+++ b/src/Analyser.php
@@ -118,6 +118,13 @@ class Analyser
      */
     private $extensionSymbols;
 
+    /**
+     * lowercase symbol name => kind
+     *
+     * @var array<string, SymbolKind::*>
+     */
+    private $extensionSymbolKinds;
+
     /**
      * @param array<string, ClassLoader> $classLoaders vendorDir => ClassLoader (e.g. result of \Composer\Autoload\ClassLoader::getRegisteredLoaders())
      * @param array<string, bool> $composerJsonDependencies package or ext-* => is dev dependency
@@ -385,9 +392,7 @@ private function getUsedSymbolsInFile(string $filePath): array
         }
 
         return (new UsedSymbolExtractor($code))->parseUsedSymbols(
-            array_keys($this->extensionSymbols[SymbolKind::CLASSLIKE]),
-            array_keys($this->extensionSymbols[SymbolKind::FUNCTION]),
-            array_keys($this->extensionSymbols[SymbolKind::CONSTANT])
+            $this->extensionSymbolKinds
         );
     }
 
@@ -547,6 +552,7 @@ private function initExistingSymbols(): void
                         $this->ignoredSymbols[$constantName] = true;
                     } else {
                         $this->extensionSymbols[SymbolKind::CONSTANT][$constantName] = $extensionName;
+                        $this->extensionSymbolKinds[$constantName] = SymbolKind::CONSTANT;
                     }
                 }
             }
@@ -568,6 +574,7 @@ private function initExistingSymbols(): void
                         $this->ignoredSymbols[$functionName] = true;
                     } else {
                         $this->extensionSymbols[SymbolKind::FUNCTION][$functionName] = $extensionName;
+                        $this->extensionSymbolKinds[$functionName] = SymbolKind::FUNCTION;
                     }
                 }
             }
@@ -590,6 +597,7 @@ private function initExistingSymbols(): void
                         $this->ignoredSymbols[$classLikeName] = true;
                     } else {
                         $this->extensionSymbols[SymbolKind::CLASSLIKE][$classLikeName] = $extensionName;
+                        $this->extensionSymbolKinds[strtolower($classLikeName)] = SymbolKind::CLASSLIKE;
                     }
                 }
             }
diff --git a/src/UsedSymbolExtractor.php b/src/UsedSymbolExtractor.php
index 74d007c..b16a27f 100644
--- a/src/UsedSymbolExtractor.php
+++ b/src/UsedSymbolExtractor.php
@@ -2,9 +2,6 @@
 
 namespace ShipMonk\ComposerDependencyAnalyser;
 
-use function array_fill_keys;
-use function array_map;
-use function array_merge;
 use function count;
 use function explode;
 use function is_array;
@@ -70,24 +67,15 @@ public function __construct(string $code)
      * It does not produce any local names in current namespace
      * - this results in very limited functionality in files without namespace
      *
-     * @param list<string> $extClasses
-     * @param list<string> $extFunctions
-     * @param list<string> $extConstants
+     * @param array<string, SymbolKind::*> $extensionSymbols
      * @return array<SymbolKind::*, array<string, list<int>>>
      * @license Inspired by https://github.com/doctrine/annotations/blob/2.0.0/lib/Doctrine/Common/Annotations/TokenParser.php
      */
     public function parseUsedSymbols(
-        array $extClasses,
-        array $extFunctions,
-        array $extConstants
+        array $extensionSymbols
     ): array
     {
         $usedSymbols = [];
-        $extensionSymbols = array_merge(
-            array_fill_keys(array_map('strtolower', $extClasses), SymbolKind::CLASSLIKE),
-            array_fill_keys(array_map('strtolower', $extFunctions), SymbolKind::FUNCTION),
-            array_fill_keys(array_map('strtolower', $extConstants), SymbolKind::CONSTANT)
-        );
         $useStatements = [];
         $useStatementKinds = [];
 
diff --git a/tests/UsedSymbolExtractorTest.php b/tests/UsedSymbolExtractorTest.php
index 74192a4..016b605 100644
--- a/tests/UsedSymbolExtractorTest.php
+++ b/tests/UsedSymbolExtractorTest.php
@@ -3,8 +3,8 @@
 namespace ShipMonk\ComposerDependencyAnalyser;
 
 use PHPUnit\Framework\TestCase;
-use function array_map;
 use function file_get_contents;
+use function strtolower;
 use const PHP_VERSION_ID;
 
 class UsedSymbolExtractorTest extends TestCase
@@ -24,9 +24,15 @@ public function test(string $path, array $expectedUsages): void
         self::assertSame(
             $expectedUsages,
             $extractor->parseUsedSymbols(
-                ['PDO'],
-                array_map('strtolower', ['json_encode', 'DDTrace\active_span', 'DDTrace\root_span']),
-                ['LIBXML_ERR_FATAL', 'LIBXML_ERR_ERROR', 'DDTrace\DBM_PROPAGATION_FULL']
+                [
+                    strtolower('PDO') => SymbolKind::CLASSLIKE,
+                    strtolower('json_encode') => SymbolKind::FUNCTION,
+                    strtolower('DDTrace\active_span') => SymbolKind::FUNCTION,
+                    strtolower('DDTrace\root_span') => SymbolKind::FUNCTION,
+                    strtolower('LIBXML_ERR_FATAL') => SymbolKind::CONSTANT,
+                    strtolower('LIBXML_ERR_ERROR') => SymbolKind::CONSTANT,
+                    strtolower('DDTrace\DBM_PROPAGATION_FULL') => SymbolKind::CONSTANT,
+                ]
             )
         );
     }