diff --git a/libs/wine/string.c b/libs/wine/string.c
index 8f85c632062..0b42ea8a8cc 100644
--- a/libs/wine/string.c
+++ b/libs/wine/string.c
@@ -351,7 +351,7 @@ int vsnprintfW(WCHAR *str, size_t len, const WCHAR *format, va_list valist)
 {
     unsigned int written = 0;
     const WCHAR *iter = format;
-    char bufa[256], fmtbufa[64], *fmta;
+    char bufa[512], fmtbufa[64], *fmta;
 
     while (*iter)
     {