diff --git a/pkt-line.c b/pkt-line.c
index bd603f8721..295ba2b16c 100644
--- a/pkt-line.c
+++ b/pkt-line.c
@@ -129,7 +129,7 @@ int packet_read_line(int fd, char *buffer, unsigned size)
 	safe_read(fd, linelen, 4);
 	len = packet_length(linelen);
 	if (len < 0)
-		die("protocol error: bad line length character");
+		die("protocol error: bad line length character: %.4s", linelen);
 	if (!len)
 		return 0;
 	len -= 4;