diff --git a/lib/cache.h b/lib/cache.h
index 4243c1bc3528e6505ba7044645c60696162c87b2..211eb20cf5754112083a43b611409610fec8e8cb 100644
--- a/lib/cache.h
+++ b/lib/cache.h
@@ -39,7 +39,8 @@ enum kr_cache_rank {
 	KR_RANK_INSECURE  = 1,  /* Entry is DNSSEC insecure (e.g. RRSIG not exists). */
 	KR_RANK_NONAUTH   = 8,  /* Entry from authority section (i.e. parent-side) */
 	KR_RANK_AUTH      = 16, /* Entry from answer (authoritative data) */
-	KR_RANK_SECURE    = 256,  /* Entry is DNSSEC valid (e.g. RRSIG exists). */
+	KR_RANK_SECURE    = 64, /* Entry is DNSSEC valid (e.g. RRSIG exists). */
+	/* @note Rank must not exceed 6 bits */
 };
 
 /**