diff --git a/plugins/mgmtops.c b/plugins/mgmtops.c
index 5e89046..95de3d1 100644
--- a/plugins/mgmtops.c
+++ b/plugins/mgmtops.c
@@ -501,7 +501,7 @@
 	char addr[18];
 
 	ba2str(bdaddr, addr);
-	DBG("index %d addr %s pinlen %lu", index, addr, pin_len);
+	DBG("index %d addr %s pinlen %zu", index, addr, pin_len);
 
 	memset(buf, 0, sizeof(buf));