diff --git a/request.go b/request.go
index 63bf0f1..726be76 100644
--- a/request.go
+++ b/request.go
@@ -82,13 +82,16 @@ func Request(ctx context.Context, respStruct interface{}, opts RequestOpts) (*ht
 }
 
 func SilentProxy(ctx context.Context, w http.ResponseWriter, resp *http.Response) {
-	w.Header().Set("Content-Type", "application/json")
-
 	for key, valueSlice := range resp.Header {
 		for _, v := range valueSlice {
 			w.Header().Add(key, v)
 		}
 	}
+
+	if w.Header().Get("Content-Type") == "" {
+		w.Header().Set("Content-Type", "application/json")
+	}
+
 	w.WriteHeader(resp.StatusCode)
 
 	if resp.Body == nil {