diff --git a/src/net/http/httputil/reverseproxy.go b/src/net/http/httputil/reverseproxy.go
index 1d45e4c49f1..46e5f68a843 100644
--- a/src/net/http/httputil/reverseproxy.go
+++ b/src/net/http/httputil/reverseproxy.go
@@ -402,11 +402,15 @@ func (p *ReverseProxy) flushInterval(res *http.Response) time.Duration {
 
 	// For Server-Sent Events responses, flush immediately.
 	// The MIME type is defined in https://www.w3.org/TR/eventsource/#text-event-stream
-	// We might have the case of streaming for which Content-Length might be unset.
-	if resCT == "text/event-stream" || res.ContentLength == -1 {
+	if resCT == "text/event-stream" {
 		return -1 // negative means immediately
 	}
 
+	// We might have the case of streaming for which Content-Length might be unset.
+	if res.ContentLength == -1 {
+		return -1
+	}
+
 	return p.FlushInterval
 }