diff --git a/lib/stream.c b/lib/stream.c
index b378ab62a5..fcfbc78e3d 100644
--- a/lib/stream.c
+++ b/lib/stream.c
@@ -1122,7 +1122,7 @@ int stream_flush(struct stream *s, int fd)
 	return nbytes;
 }
 
-void stream_hexdump(struct stream *s)
+void stream_hexdump(const struct stream *s)
 {
 	zlog_hexdump(s->data, s->endp);
 }
diff --git a/lib/stream.h b/lib/stream.h
index f84f028852..23d83bf930 100644
--- a/lib/stream.h
+++ b/lib/stream.h
@@ -253,7 +253,7 @@ extern int stream_flush(struct stream *, int);
 extern int stream_empty(struct stream *); /* is the stream empty? */
 
 /* debugging */
-extern void stream_hexdump(struct stream *);
+extern void stream_hexdump(const struct stream *s);
 
 /* deprecated */
 extern uint8_t *stream_pnt(struct stream *);