diff --git a/test/test-stress.c b/test/test-stress.c
index f1c8b2e1..7d8993a0 100644
--- a/test/test-stress.c
+++ b/test/test-stress.c
@@ -38,7 +38,7 @@ static bool   allow_large_objects = true;    // allow very large objects?
 static size_t use_one_size = 0;              // use single object size of `N * sizeof(uintptr_t)`?
 
 
-#ifndef USE_STD_MALLOC
+#ifdef USE_STD_MALLOC
 #define custom_calloc(n,s)    calloc(n,s)
 #define custom_realloc(p,s)   realloc(p,s)
 #define custom_free(p)        free(p)