diff --git a/src/stdio/ext.c b/src/stdio/ext.c
index d5a403b6a03abb4a860398958f741057dd0ed0f4..6b8ce91c5eb2a9fca45a8a9771ccea99452b5152 100644
--- a/src/stdio/ext.c
+++ b/src/stdio/ext.c
@@ -14,7 +14,7 @@ int __fsetlocking(FILE *f, int type)
 
 int __fwriting(FILE *f)
 {
-	return f->wend > f->wpos;
+	return f->wend && f->wpos > f->wbase;
 }
 
 int __freading(FILE *f)