diff --git a/lib/dns/adb.c b/lib/dns/adb.c
index aee7b85c49..ef7875dcb4 100644
--- a/lib/dns/adb.c
+++ b/lib/dns/adb.c
@@ -1286,6 +1286,7 @@ clean_namehooks(dns_adb_t *adb, dns_adbnamehooklist_t *namehooks) {
 				if (addr_bucket != DNS_ADB_INVALIDBUCKET)
 					UNLOCK(&adb->entrylocks[addr_bucket]);
 				addr_bucket = entry->lock_bucket;
+				INSIST(addr_bucket != DNS_ADB_INVALIDBUCKET);
 				LOCK(&adb->entrylocks[addr_bucket]);
 			}