diff --git a/CHANGELOG b/CHANGELOG
index 84bba88..c9204ab 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,6 @@
 v0.7.2 (unreleased):
 
-- ...
+- Fix building on non-CPython implementations like PyPy. (#341)
 
 v0.7.1 (released June 30, 2025):
 
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 89d27fb..4fe3949 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -7,7 +7,8 @@ v0.7.2
 Unreleased
 (`changes <https://github.com/earwig/mwparserfromhell/compare/v0.7.1...main>`__):
 
-- ...
+- Fix building on non-CPython implementations like PyPy.
+  (`#341 <https://github.com/earwig/mwparserfromhell/issues/341>`_)
 
 v0.7.1
 ------
diff --git a/setup.py b/setup.py
index 5cfc667..cd14eda 100644
--- a/setup.py
+++ b/setup.py
@@ -24,6 +24,7 @@ from __future__ import annotations
 
 import glob
 import os
+import platform
 import sys
 from enum import Enum
 
@@ -63,8 +64,10 @@ elif "WITHOUT_EXTENSION" in os.environ:
             f"Unknown value for $WITHOUT_EXTENSION; should be '1', or '0', "
             f"but found {value!r}"
         )
-else:
+elif platform.python_implementation() == "CPython":
     use_extension = UseExtension.REQUIRED
+else:
+    use_extension = UseExtension.IGNORED
 
 if use_extension == UseExtension.IGNORED:
     ext_modules = []