diff --git a/src/alloc-override-osx.c b/src/alloc-override-osx.c
index a88186bc..9c331cae 100644
--- a/src/alloc-override-osx.c
+++ b/src/alloc-override-osx.c
@@ -43,7 +43,7 @@ extern malloc_zone_t* malloc_default_purgeable_zone(void) __attribute__((weak_im
 
 static size_t zone_size(malloc_zone_t* zone, const void* p) {
   MI_UNUSED(zone);
-  //if (!mi_is_in_heap_region(p)){ return 0; } // not our pointer, bail out
+  if (!mi_is_in_heap_region(p)){ return 0; } // not our pointer, bail out
   return mi_usable_size(p);
 }