diff --git a/MANIFEST.in b/MANIFEST.in
index 84b86e89..887e4e97 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,5 +1,5 @@
 exclude *.py
-include setup.py build.py
+include setup.py build.py run_tests.py
 include LICENSE README.rst
 include gumbo/*.c gumbo/*.h gumbo/*.py gumbo/*.rl
 include src/*.c src/*.h