diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 32d1f80..c77167a 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -30,7 +30,7 @@ jobs:
         run: poetry install --extras turbo
 
       - name: Run Tests (With Extension Modules)
-        run: poetry run pytest -q tests
+        run: poetry run pytest -q tests --turbo=1
 
       - name: Upload coverage to Codecov
         uses: codecov/codecov-action@v2
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 871effd..c803ed6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ## [0.2.6] - Unreleased
 - Added `KY` and `MM` to valid prefixes
+- Added support to check for compiled extension modules
 
 ## [0.2.5] - 2022-04-10
 - Fixed missing `jcs` dependency
diff --git a/docs/changelog.md b/docs/changelog.md
index 871effd..c803ed6 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -2,6 +2,7 @@
 
 ## [0.2.6] - Unreleased
 - Added `KY` and `MM` to valid prefixes
+- Added support to check for compiled extension modules
 
 ## [0.2.5] - 2022-04-10
 - Fixed missing `jcs` dependency
diff --git a/iscc_core/check.py b/iscc_core/check.py
new file mode 100644
index 0000000..ef4a6d5
--- /dev/null
+++ b/iscc_core/check.py
@@ -0,0 +1,38 @@
+# -*- coding: utf-8 -*-
+"""Inspect lib environment/installation"""
+import importlib.machinery
+import inspect
+
+
+EXTENSION_SUFFIXES = tuple(sf.lstrip(".") for sf in importlib.machinery.EXTENSION_SUFFIXES)
+
+
+def suffix(filename):
+    return "." in filename and filename.rpartition(".")[-1] or ""
+
+
+def isnativemodule(module):
+    """isnativemodule(thing) → boolean predicate, True if `module`
+    is a native-compiled (“extension”) module.
+
+    Q.v. this fine StackOverflow answer on this subject:
+        https://stackoverflow.com/a/39304199/298171
+    """
+    # Step one: modules only beyond this point:
+    if not inspect.ismodule(module):  # pragma: no cover
+        return False
+
+    # Step two: return truly when “__loader__” is set:
+    if isinstance(
+        getattr(module, "__loader__", None), importlib.machinery.ExtensionFileLoader
+    ):  # pragma: no cover
+        return True
+
+    # Step three: in leu of either of those indicators,
+    # check the module path’s file suffix:
+    try:
+        ext = suffix(inspect.getfile(module))
+    except TypeError as exc:
+        return "is a built-in" in str(exc)
+
+    return ext in EXTENSION_SUFFIXES
diff --git a/tests/conftest.py b/tests/conftest.py
index 1656a57..81a5c92 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -5,6 +5,17 @@
 MB1 = 1024 * 1024
 
 
+def pytest_addoption(parser):
+    parser.addoption(
+        "--turbo", action="store_true", default=False, help="run extension module tests"
+    )
+
+
+@pytest.fixture
+def turbo(request):
+    return request.config.getoption("--turbo")
+
+
 @pytest.fixture(scope="module", name="static_bytes")
 def static_bytes_(n: int = MB1, block_size: int = 4) -> bytes:
     """Wraps static_bytes function as a fixture (both can be used)."""
diff --git a/tests/test_check.py b/tests/test_check.py
new file mode 100644
index 0000000..f11f395
--- /dev/null
+++ b/tests/test_check.py
@@ -0,0 +1,24 @@
+# -*- coding: utf-8 -*-
+from iscc_core import cdc, minhash, simhash
+from iscc_core import check
+import array
+
+
+def test_check_suffix():
+    assert check.suffix("hello.world") == "world"
+
+
+def test_check_isnativemodule():
+    assert check.isnativemodule(check) is False
+    assert check.isnativemodule(array) is True
+
+
+def test_check_turbo(turbo):
+    if turbo is False:
+        assert check.isnativemodule(cdc) is False
+        assert check.isnativemodule(simhash) is False
+        assert check.isnativemodule(minhash) is False
+    else:
+        assert check.isnativemodule(cdc) is True
+        assert check.isnativemodule(simhash) is True
+        assert check.isnativemodule(minhash) is True