diff --git a/doc/internals/filters.txt b/doc/internals/filters.txt
index 75c640c..7b5144a 100644
--- a/doc/internals/filters.txt
+++ b/doc/internals/filters.txt
@@ -229,7 +229,7 @@
                                     struct http_msg *msg);
         void (*http_reply)         (struct stream *s, struct filter *f,
                                     short status,
-                                    const struct chunk *msg);
+                                    const struct buffer *msg);
 
         /*
          * TCP callbacks