diff --git a/dlls/msvcp90/locale.c b/dlls/msvcp90/locale.c
index b37ead4c884..5a5e39cc755 100644
--- a/dlls/msvcp90/locale.c
+++ b/dlls/msvcp90/locale.c
@@ -9704,6 +9704,7 @@ size_t __cdecl mbsrtowcs(wchar_t *dst, const char **pstr, size_t n, mbstate_t *s
     {
         *_errno() = EINVAL;
         _invalid_parameter( NULL, NULL, NULL, 0, 0 );
+        return -1;
     }
     src = *pstr;
     if (!state) state = &local_state;
@@ -9747,6 +9748,7 @@ size_t __cdecl wcsrtombs(char *dst, const wchar_t **pstr, size_t n, mbstate_t *s
     {
         *_errno() = EINVAL;
         _invalid_parameter( NULL, NULL, NULL, 0, 0 );
+        return -1;
     }
     src = *pstr;