diff --git a/reactos/lib/msvcrt/msvcrt.def b/reactos/lib/msvcrt/msvcrt.def
index 225201e8d2f..c5577289281 100644
--- a/reactos/lib/msvcrt/msvcrt.def
+++ b/reactos/lib/msvcrt/msvcrt.def
@@ -528,7 +528,7 @@ _strrev
 _strset
 _strtime
 _strtoi64=stub
-_strtoui64=stub
+_strtoui64=strtoull
 _strupr
 _swab
 _sys_errlist DATA