diff --git a/libc/include/stdlib.h b/libc/include/stdlib.h
index be2496b4..253c8e5c 100644
--- a/libc/include/stdlib.h
+++ b/libc/include/stdlib.h
@@ -106,6 +106,9 @@ int mblen(const char*, size_t);
 size_t mbstowcs(wchar_t* __restrict, const char* __restrict, size_t);
 int mbtowc(wchar_t *__restrict, const char* __restrict, size_t);
 int mkstemp(char*);
+#if !defined(__is_sortix_libc) /* not a warning inside libc */
+__attribute__((__warning__("mktemp() is racy, use mkstemp()")))
+#endif
 char* mktemp(char* templ);
 int on_exit(void (*function)(int, void*), void* arg);
 void qsort(void*, size_t, size_t, int (*)(const void*, const void*));