diff --git a/source/performance.txt b/source/performance.txt
index d0cf8619db8679c98c49a8466068d1da7f329700_c291cmNlL3BlcmZvcm1hbmNlLnR4dA==..c5e375d23dae326525b80f761622cb2b440c8f52_c291cmNlL3BlcmZvcm1hbmNlLnR4dA== 100644
--- a/source/performance.txt
+++ b/source/performance.txt
@@ -32,6 +32,8 @@
 
 * **Building very large dicts**
 
+* CPython C extension modules
+
 XXX
 
 We generally consider things that are slower on PyPy than CPython PyPy's bugs.