diff --git a/WINGs/wfilepanel.c b/WINGs/wfilepanel.c
index 372683f3..9e8fdff0 100644
--- a/WINGs/wfilepanel.c
+++ b/WINGs/wfilepanel.c
@@ -589,7 +589,7 @@ static void showError(WMScreen * scr, WMWindow * owner, const char *s, const cha
 	char *errStr;
 
 	if (file) {
-		errStr = wmalloc(strlen(file) + strlen(s));
+		errStr = wmalloc(strlen(file) + strlen(s) + 1);
 		sprintf(errStr, s, file);
 	} else {
 		errStr = wstrdup(s);