diff --git a/Python/ceval.c b/Python/ceval.c
index 8ec00bc..abdea1d 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -7,6 +7,7 @@
    */
 
 /* enable more aggressive intra-module optimizations, where available */
+/* affects both release and debug builds - see bpo-43271 */
 #define PY_LOCAL_AGGRESSIVE
 
 #include "Python.h"