diff --git a/pkt-line.c b/pkt-line.c
index 0477d2eef..e75af023b 100644
--- a/pkt-line.c
+++ b/pkt-line.c
@@ -24,7 +24,7 @@ static void packet_trace(const char *buf, unsigned int len, int write)
 	strbuf_addf(&out, "packet: %12s%c ",
 		    packet_trace_prefix, write ? '>' : '<');
 
-	if (starts_with(buf, "PACK") || starts_with(buf + 1, "PACK")) {
+	if (starts_with(buf, "PACK") || starts_with(buf, "\1PACK")) {
 		strbuf_addstr(&out, "PACK ...");
 		trace_disable(&trace_packet);
 	}