diff --git a/pkg/rest/api.go b/pkg/rest/api.go
index cbcfc378..36548b3c 100644
--- a/pkg/rest/api.go
+++ b/pkg/rest/api.go
@@ -147,12 +147,12 @@ func PutConfig(w http.ResponseWriter, r *http.Request) {
 func DoProxy(w http.ResponseWriter, r *http.Request) {
 	target := r.Header.Get("X-Target-Uri")
 	if target == "" {
-		WriteJson(w, model.NewErrorResult("param invalid: X-Target-Uri", model.CodeInvalidParam))
+		writeError(w, "param invalid: X-Target-Uri")
 		return
 	}
 	targetUrl, err := url.Parse(target)
 	if err != nil {
-		WriteJson(w, model.NewErrorResult(err.Error()))
+		writeError(w, err.Error())
 		return
 	}
 	r.RequestURI = ""
@@ -160,7 +160,7 @@ func DoProxy(w http.ResponseWriter, r *http.Request) {
 	r.Host = targetUrl.Host
 	resp, err := http.DefaultClient.Do(r)
 	if err != nil {
-		WriteJson(w, model.NewErrorResult(err.Error()))
+		writeError(w, err.Error())
 		return
 	}
 	defer resp.Body.Close()
@@ -179,11 +179,16 @@ func DoProxy(w http.ResponseWriter, r *http.Request) {
 		reader = resp.Body
 	}
 	if _, err := io.Copy(w, reader); err != nil {
-		WriteJson(w, model.NewErrorResult(err.Error()))
+		writeError(w, err.Error())
 		return
 	}
 }
 
+func writeError(w http.ResponseWriter, msg string) {
+	w.WriteHeader(http.StatusInternalServerError)
+	w.Write([]byte(msg))
+}
+
 func getServerConfig() *download.DownloaderStoreConfig {
 	_, cfg, _ := Downloader.GetConfig()
 	return cfg
diff --git a/pkg/rest/server_test.go b/pkg/rest/server_test.go
index 748c7e7e..cb3d4da2 100644
--- a/pkg/rest/server_test.go
+++ b/pkg/rest/server_test.go
@@ -229,6 +229,15 @@ func TestDoProxy(t *testing.T) {
 			t.Errorf("DoProxy() got = %v, want %v", got, want)
 		}
 	})
+
+	doTest(func() {
+		code, _ := doHttpRequest0(http.MethodGet, "/api/v1/proxy", map[string]string{
+			"X-Target-Uri": "https://github.com/GopeedLab/gopeed/raw/695da7ea87d2b455552b709d3cb4d7879484d4d1/NOT_FOUND",
+		}, nil)
+		if code != http.StatusNotFound {
+			t.Errorf("DoProxy() got = %v, want %v", code, http.StatusNotFound)
+		}
+	})
 }
 
 func TestAuthorization(t *testing.T) {
@@ -307,14 +316,15 @@ func doHttpRequest0(method string, path string, headers map[string]string, body
 	if err != nil {
 		panic(err)
 	}
-	if response.StatusCode != http.StatusOK {
-		panic(fmt.Sprintf("http request failed, status code: %d", response.StatusCode))
-	}
+
 	return response.StatusCode, respBody
 }
 
 func doHttpRequest[T any](method string, path string, headers map[string]string, body any) (int, *model.Result[T]) {
-	_, respBody := doHttpRequest0(method, path, headers, body)
+	statusCode, respBody := doHttpRequest0(method, path, headers, body)
+	if statusCode != http.StatusOK {
+		panic(fmt.Sprintf("http request failed, status code: %d", statusCode))
+	}
 
 	var r model.Result[T]
 	if err := json.Unmarshal(respBody, &r); err != nil {
diff --git a/ui/flutter/lib/app/modules/app/controllers/app_controller.dart b/ui/flutter/lib/app/modules/app/controllers/app_controller.dart
index e75f6864..ec2b03e7 100644
--- a/ui/flutter/lib/app/modules/app/controllers/app_controller.dart
+++ b/ui/flutter/lib/app/modules/app/controllers/app_controller.dart
@@ -120,7 +120,7 @@ class AppController extends GetxController {
       var allFail = true;
       for (var cdn in allTrackerSubscribeUrlCdns[u]!) {
         try {
-          result.addAll(await _fetchTrackers(u));
+          result.addAll(await _fetchTrackers(cdn));
           allFail = false;
           break;
         } catch (e) {
@@ -168,10 +168,14 @@ class AppController extends GetxController {
   Future<List<String>> _fetchTrackers(String subscribeUrl) async {
     final resp = await proxyRequest(subscribeUrl);
     if (resp.statusCode != 200) {
-      throw Exception('Failed to get trackers');
+      throw Exception(
+          'Failed to get trackers, status code: ${resp.statusCode}');
+    }
+    if (resp.data == null || resp.data!.isEmpty) {
+      throw Exception('Failed to get trackers, data is null');
     }
     const ls = LineSplitter();
-    return ls.convert(resp.data).where((e) => e.isNotEmpty).toList();
+    return ls.convert(resp.data!).where((e) => e.isNotEmpty).toList();
   }
 
   _initDownloaderConfig() async {