diff --git a/reactos/lib/sdk/crt/stdlib/atexit.c b/reactos/lib/sdk/crt/stdlib/atexit.c
index 5ed0fc0e1ca..6e52c66cf49 100644
--- a/reactos/lib/sdk/crt/stdlib/atexit.c
+++ b/reactos/lib/sdk/crt/stdlib/atexit.c
@@ -44,7 +44,7 @@ _onexit_t CDECL __dllonexit(_onexit_t func, _onexit_t **start, _onexit_t **end)
   if (++len <= 0)
     return NULL;
 
-  tmp = realloc(*start, len * sizeof(tmp));
+  tmp = realloc(*start, len * sizeof(_onexit_t));
   if (!tmp)
     return NULL;
   *start = tmp;