diff --git a/docs/topics/signals.rst b/docs/topics/signals.rst
index a67cc1879..63ad3a9ad 100644
--- a/docs/topics/signals.rst
+++ b/docs/topics/signals.rst
@@ -413,7 +413,7 @@ headers_received
 .. versionadded:: 2.5
 
 .. signal:: headers_received
-.. function:: headers_received(headers, request, spider)
+.. function:: headers_received(headers, body_length, request, spider)
 
     Sent by the HTTP 1.1 and S3 download handlers when the response headers are
     available for a given request, before downloading any additional content.