diff --git a/.github/static/check_nbextensions.py b/.github/static/check_nbextensions.py
new file mode 100755
index 0000000..1ec62aa
--- /dev/null
+++ b/.github/static/check_nbextensions.py
@@ -0,0 +1,66 @@
+#!/usr/bin/env python3
+import json
+from pathlib import Path
+import subprocess
+from typing import List, Union
+
+
+def assert_extension(extensions: List[str]) -> None:
+    """Assert specific extension exists in the list of installed and enabled notebook extensions.
+
+    "Validating: OK" will go to stderr, while the list of enabled extensions go to stdout.
+    """
+    extensions_list_call = subprocess.run(
+        ["jupyter", "nbextension", "list"],
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+    )
+    nbextensions = [
+        _ for _ in extensions_list_call.stdout.decode().splitlines() if " " * 6 in _
+    ]
+    enabled_nbextensions = [_ for _ in nbextensions if "enabled" in _]
+    validations = extensions_list_call.stderr.decode().splitlines()
+
+    for extension in extensions:
+        assert extension in "".join(
+            nbextensions
+        ), f"{extension!r} not found in list of installed Jupyter NB extensions: {extensions_list_call.stdout.decode()}"
+        assert extension in "".join(
+            enabled_nbextensions
+        ), f"{extension!r} not found to be an enabled Jupyter NB extension: {extensions_list_call.stdout.decode()}"
+        for index, nbextension in enumerate(nbextensions):
+            if extension in nbextension:
+                assert "OK" in validations[index], (
+                    f"{extension!r} not found to be validated. Validations and output: "
+                    f"{extensions_list_call.stderr.decode()}\n{extensions_list_call.stdout.decode()}"
+                )
+                break
+        else:
+            raise RuntimeError(
+                f"By now, the extension {extension!r} should known to be an installed Jupyter NB "
+                "extension, but was not found in the list of Jupyter NB extensions: "
+                f"{extensions_list_call.stdout.decode()}"
+            )
+
+
+def get_extension_name(json_file: Union[str, Path]) -> List[str]:
+    """Retrieve extension name from `json_file`"""
+    if not isinstance(json_file, Path):
+        json_file = Path(json_file).resolve()
+    if not json_file.exists():
+        raise RuntimeError(f"Could not find requested extension file at {json_file!r}")
+
+    with open(json_file, "r") as handle:
+        extension_file: dict = json.load(handle)
+
+    return [_ for _ in extension_file.get("load_extensions", {})]
+
+
+if __name__ == "__main__":
+    extension_file = (
+        Path(__file__)
+        .resolve()
+        .parent.parent.parent.joinpath("ipywidgets_extended.json")
+    )
+    extension = get_extension_name(extension_file)
+    assert_extension(extension)
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2d35da0..cd47dab 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -47,22 +47,25 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node-version: ['10', '12']
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        node-version: ['10', '13']
+        python-version: [3.6, 3.9]
 
     steps:
     - name: Checkout repository
       uses: actions/checkout@v2
 
-    - name: Install Node ${{ matrix.node-version}}
+    - name: Install Node ${{ matrix.node-version }}
       uses: actions/setup-node@v1
       with:
-        node-version: ${{ matrix.node-version}}
+        node-version: ${{ matrix.node-version }}
 
-    - name: Set up Python ${{ matrix.python-version}}
+    - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v2
       with:
-        python-version: ${{ matrix.python-version}}
+        python-version: ${{ matrix.python-version }}
+
+    - name: Install Python requirements
+      run: pip install -r requirements.txt
 
     - name: Check build and installation of PyPI source distribution
       env:
@@ -75,3 +78,6 @@ jobs:
         mkdir -p /tmp/installation_dir
         cd /tmp/installation_dir
         pip install ${ORIGINAL_PWD}/${SDIST_DIR}/${SDIST_FILE}
+
+    - name: Assert nbextension installed correctly
+      run: ./.github/static/check_nbextensions.py
diff --git a/.github/workflows/publish-on-pypi.yml b/.github/workflows/publish-on-pypi.yml
index 5d6616b..aa3c437 100644
--- a/.github/workflows/publish-on-pypi.yml
+++ b/.github/workflows/publish-on-pypi.yml
@@ -16,15 +16,21 @@ jobs:
     - name: Checkout repository
       uses: actions/checkout@v2
 
+    - name: Install Node 13
+      uses: actions/setup-node@v1
+      with:
+        node-version: '13'
+
     - name: Set up Python 3.9
       uses: actions/setup-python@v2
       with:
         python-version: 3.9
 
-    - name: Update setuptools
+    - name: Update setuptools and install requirements
       run: |
         python -m pip install --upgrade pip
         pip install -U setuptools
+        pip install -r requirements.txt
 
     - name: Update version and tag
       run: .github/static/update_version.sh
diff --git a/MANIFEST.in b/MANIFEST.in
index 9c4c175..c13c667 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,7 +1,31 @@
 include LICENSE
 include README.md
 include requirements*.txt
+
 include setupbase.py
-include *.json
-include *.js
-recursive-include src *.ts
+
+include tsconfig.json
+include package.json
+include webpack.config.js
+include ipywidgets_extended/labextension/*.tgz
+
+# Examples
+graft examples
+
+# Tests
+graft tests
+prune tests/build
+
+# Javascript files
+graft ipywidgets_extended/nbextension
+graft src
+prune **/node_modules
+prune coverage
+prune lib
+
+# Patterns to exclude from any directory
+global-exclude *~
+global-exclude *.pyc
+global-exclude *.pyo
+global-exclude .git
+global-exclude .ipynb_checkpoints
diff --git a/ipywidgets_extended.json b/ipywidgets_extended.json
index 85d76d5..ef48c66 100644
--- a/ipywidgets_extended.json
+++ b/ipywidgets_extended.json
@@ -1,5 +1,5 @@
 {
   "load_extensions": {
-    "ipywidgets-extended/extension": true
+    "ipywidgets_extended/extension": true
   }
 }
diff --git a/ipywidgets_extended/dropdown.py b/ipywidgets_extended/dropdown.py
index bd80657..baf469f 100644
--- a/ipywidgets_extended/dropdown.py
+++ b/ipywidgets_extended/dropdown.py
@@ -20,10 +20,10 @@ class DropdownExtended(Dropdown):
 
     _model_name = traitlets.Unicode("DropdownExtendedModel").tag(sync=True)
     _model_module = traitlets.Unicode("ipywidgets-extended").tag(sync=True)
-    _model_module_version = traitlets.Unicode(__version__).tag(sync=True)
+    _model_module_version = traitlets.Unicode(f"^{__version__}").tag(sync=True)
     _view_name = traitlets.Unicode("DropdownExtendedView").tag(sync=True)
     _view_module = traitlets.Unicode("ipywidgets-extended").tag(sync=True)
-    _view_module_version = traitlets.Unicode(__version__).tag(sync=True)
+    _view_module_version = traitlets.Unicode(f"^{__version__}").tag(sync=True)
 
     # This being read-only means that it cannot be changed by the user.
     _disabled_options_labels = traitlets.List(
diff --git a/package.json b/package.json
index b22f4ae..19f7b8e 100644
--- a/package.json
+++ b/package.json
@@ -4,8 +4,6 @@
   "description": "Extensions to the Jupyter Widgets in the 'ipywidgets' pacakge.",
   "keywords": [
     "jupyter",
-    "jupyterlab",
-    "jupyterlab-extension",
     "widgets"
   ],
   "files": [
@@ -48,7 +46,7 @@
     "watch:nbextension": "webpack --watch"
   },
   "dependencies": {
-    "@jupyter-widgets/base": "^1.2.0 || ^2 || ^3",
+    "@jupyter-widgets/base": "^1.2.0 || ^2 || ^3 || ^4",
     "@jupyter-widgets/controls": "^1.5.0 || ^2 || ^3"
   },
   "devDependencies": {
diff --git a/setup.py b/setup.py
index b0dcd1c..2264fd3 100644
--- a/setup.py
+++ b/setup.py
@@ -50,7 +50,7 @@
 )
 
 setup(
-    name="ipywidgets-extended",
+    name=NAME.replace("_", "-"),
     version=get_version(Path(NAME) / "version.py"),
     license="BSD",
     author="Casper Welzel Andersen",
diff --git a/tsconfig.json b/tsconfig.json
index e483763..75169a2 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -16,6 +16,7 @@
     "target": "es2015"
   },
   "include": [
-    "src/*.ts"
+    "src/**/*.ts",
+    "src/**/*.tsx"
   ]
 }
diff --git a/webpack.config.js b/webpack.config.js
index e3ca1e1..a1e3ae2 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -9,7 +9,7 @@ const rules = [
 ];
 
 // Packages that shouldn't be bundled but loaded at runtime
-const externals = ['@jupyter-widgets/base'];
+const externals = ['@jupyter-widgets/base', '@jupyter-widgets/controls'];
 
 const resolve = {
   // Add '.ts' and '.tsx' as resolvable extensions.
@@ -55,7 +55,7 @@ module.exports = [
         path: path.resolve(__dirname, 'dist'),
         libraryTarget: 'amd',
         library: "ipywidgets-extended",
-        publicPath: 'https://unpkg.com/ipywidgets_extended@' + version + '/dist/'
+        publicPath: 'https://unpkg.com/ipywidgets-extended@' + version + '/dist/'
     },
     devtool: 'source-map',
     module: {