diff --git a/handler.go b/handler.go
index e9541e0..88b6455 100644
--- a/handler.go
+++ b/handler.go
@@ -71,10 +71,7 @@ func (cui *ConfigUI) GetDelta(w http.ResponseWriter, r *http.Request) {
 		panic(err)
 	}
 	if delta > stat.Size() {
-		panic(fmt.Errorf("delta(%d) is larger than file size(%d)", delta, stat.Size()))
-	}
-	if stat.Size() < delta {
-		panic(fmt.Errorf("delta(%d) is smaller than file size(%d)", delta, stat.Size()))
+		panic(fmt.Errorf("delta(%d) is larger than file size(%d), the file might have been changed", delta, stat.Size()))
 	}
 	buf := make([]byte, stat.Size()-delta)
 	_, err = f.ReadAt(buf, delta)
diff --git a/templates/base/script.tmpl b/templates/base/script.tmpl
index abf725b..71d6cfe 100644
--- a/templates/base/script.tmpl
+++ b/templates/base/script.tmpl
@@ -83,11 +83,12 @@ async function FileDelta(){
   else {
     const res = await fetch('{{.BaseUrl}}api/delta?f=true&name=' + Active+'&delta='+LastDelta)
       .catch(err=>{console.log(err);return;});
-    const body = await res.json();
     if(!res.ok){
-      Catch(res)
+      await Catch(res)
+      FileGet()
       return
     }
+    const body = await res.json();
     LastDelta = body.delta;
     editor.session.setValue(editor.getValue()+body.data);
   }