diff --git a/dlls/msvcp90/locale.c b/dlls/msvcp90/locale.c
index ef06172c6db..b15f1b88cad 100644
--- a/dlls/msvcp90/locale.c
+++ b/dlls/msvcp90/locale.c
@@ -10280,7 +10280,7 @@ int __cdecl wctob(wint_t wc)
 {
     char ret[MB_LEN_MAX];
 
-    if (wc == WEOF || _Wcrtomb( ret, wc, NULL, NULL ) != -1) return EOF;
+    if (wc == WEOF || _Wcrtomb( ret, wc, NULL, NULL ) != 1) return EOF;
     return ret[0];
 }