diff --git a/runner.go b/runner.go
index 2665e7c1..1e826734 100644
--- a/runner.go
+++ b/runner.go
@@ -817,6 +817,7 @@ func decodeResponseBody(resp *http.Response) error {
 			return err
 		}
 		resp.Body = gr
+		resp.ContentLength = -1 // set to unknown to avoid Content-Length mismatched
 	case "deflate":
 		resp.Body = flate.NewReader(resp.Body)
 	}