diff --git a/pkg/collect/collect.go b/pkg/collect/collect.go
index 8746184..0b18e1f 100644
--- a/pkg/collect/collect.go
+++ b/pkg/collect/collect.go
@@ -142,7 +142,11 @@ func (c *Collect) gtagHandler(l *zap.Logger, w http.ResponseWriter, r *http.Requ
 	defer resp.Body.Close()
 
 	// copy headers
-	r.Header = resp.Header.Clone()
+	for key, values := range resp.Header {
+		for _, value := range values {
+			w.Header().Add(key, value)
+		}
+	}
 
 	if _, err := io.Copy(w, resp.Body); err != nil {
 		return err
@@ -174,7 +178,11 @@ func (c *Collect) mpv2Handler(l *zap.Logger, w http.ResponseWriter, r *http.Requ
 	defer resp.Body.Close()
 
 	// copy headers
-	r.Header = resp.Header.Clone()
+	for key, values := range resp.Header {
+		for _, value := range values {
+			w.Header().Add(key, value)
+		}
+	}
 
 	if _, err := io.Copy(w, resp.Body); err != nil {
 		return err