diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index 3ff1d1fc7e3..1f583b8c78d 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -61,7 +61,7 @@ typedef struct BLOCK {
  * block is freed leaving another existing block as the new endpoint.
  */
 
-#ifdef Py_DEBUG
+#ifndef NDEBUG
 #define MARK_END(link)  link = NULL;
 #define CHECK_END(link) assert(link == NULL);
 #define CHECK_NOT_END(link) assert(link != NULL);