diff --git a/activestorage/__init__.py b/activestorage/__init__.py
index 612695e4..31f11b7f 100644
--- a/activestorage/__init__.py
+++ b/activestorage/__init__.py
@@ -1,5 +1,16 @@
 from .active import Active
 
+from importlib.metadata import version
+from importlib.metadata import PackageNotFoundError
 
-# this is used only by Readthedocs
-__version__ = "0.4.0"
+
+try:
+    __version__ = version("PyActiveStorage")
+except PackageNotFoundError as exc:
+    msg = (
+        "PyActiveStorage package not found, please run `pip install -e .` before "
+        "importing the package."
+    )
+    raise PackageNotFoundError(
+        msg,
+    ) from exc
diff --git a/environment.yml b/environment.yml
index 61efdd1b..ade4e4b7 100644
--- a/environment.yml
+++ b/environment.yml
@@ -24,6 +24,7 @@ dependencies:
   - pytest-cov >=2.10.1
   - pytest-html !=2.1.0
   - pytest-metadata >=1.5.1
+  - pytest-mock
   - pytest-xdist
   # docs
   - autodocsumm
diff --git a/pyproject.toml b/pyproject.toml
index 16c25947..6bb903c5 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -57,6 +57,7 @@ test = [
     "pytest-cov>=2.10.1",
     "pytest-html!=2.1.0",
     "pytest-metadata>=1.5.1",
+    "pytest-mock",
     "pytest-xdist",
     "dask",
     "moto",
diff --git a/tests/test_version.py b/tests/test_version.py
new file mode 100644
index 00000000..48f486bf
--- /dev/null
+++ b/tests/test_version.py
@@ -0,0 +1,29 @@
+"""Test that activestorage.__version__ returns a version number."""
+
+from __future__ import annotations
+
+import importlib
+import re
+from importlib.metadata import PackageNotFoundError
+from typing import TYPE_CHECKING
+
+import pytest
+
+import activestorage
+
+if TYPE_CHECKING:
+    from pytest_mock import MockerFixture
+
+
+def test_version():
+    assert re.match(r"^\d+\.\d+\.\d+\S*$", activestorage.__version__)
+
+
+def test_version_package_not_found_fail(mocker: MockerFixture) -> None:
+    mocker.patch(
+        "importlib.metadata.version",
+        side_effect=PackageNotFoundError("PyActiveStorage"),
+    )
+    msg = r"PyActiveStorage package not found"
+    with pytest.raises(PackageNotFoundError, match=re.escape(msg)):
+        importlib.reload(activestorage)