diff --git a/main.go b/main.go
index 4a0d88f..c2ef857 100644
--- a/main.go
+++ b/main.go
@@ -63,7 +63,7 @@ func main() {
 			case "content-length":
 			default:
 				req.Header.Set(k, v[0])
-				for _, v := range req.Header[1:] {
+				for _, v := range v[1:] {
 					req.Header.Add(k, v)
 				}
 			}