diff --git a/sys/netinet6/nd6_nbr.c b/sys/netinet6/nd6_nbr.c
index 2ac1d7a10a72..6df012ba4dcc 100644
--- a/sys/netinet6/nd6_nbr.c
+++ b/sys/netinet6/nd6_nbr.c
@@ -1217,40 +1217,26 @@ nd6_dad_start(struct ifaddr *ifa, int delay)
 	struct dadq *dp;
 	char ip6buf[INET6_ADDRSTRLEN];
 
+	KASSERT((ia->ia6_flags & IN6_IFF_TENTATIVE) != 0,
+	    ("starting DAD on non-tentative address %p", ifa));
+
 	/*
 	 * If we don't need DAD, don't do it.
 	 * There are several cases:
-	 * - DAD is disabled (ip6_dad_count == 0)
+	 * - DAD is disabled globally or on the interface
 	 * - the interface address is anycast
 	 */
-	if (!(ia->ia6_flags & IN6_IFF_TENTATIVE)) {
-		log(LOG_DEBUG,
-			"nd6_dad_start: called with non-tentative address "
-			"%s(%s)\n",
-			ip6_sprintf(ip6buf, &ia->ia_addr.sin6_addr),
-			ifa->ifa_ifp ? if_name(ifa->ifa_ifp) : "???");
-		return;
-	}
-	if (ia->ia6_flags & IN6_IFF_ANYCAST) {
+	if ((ia->ia6_flags & IN6_IFF_ANYCAST) != 0 ||
+	    V_ip6_dad_count == 0 ||
+	    (ND_IFINFO(ifa->ifa_ifp)->flags & ND6_IFF_NO_DAD) != 0) {
 		ia->ia6_flags &= ~IN6_IFF_TENTATIVE;
 		return;
 	}
-	if (!V_ip6_dad_count) {
-		ia->ia6_flags &= ~IN6_IFF_TENTATIVE;
+	if ((ifa->ifa_ifp->if_flags & IFF_UP) == 0 ||
+	    (ifa->ifa_ifp->if_drv_flags & IFF_DRV_RUNNING) == 0 ||
+	    (ND_IFINFO(ifa->ifa_ifp)->flags & ND6_IFF_IFDISABLED) != 0)
 		return;
-	}
-	if (ifa->ifa_ifp == NULL)
-		panic("nd6_dad_start: ifa->ifa_ifp == NULL");
-	if (ND_IFINFO(ifa->ifa_ifp)->flags & ND6_IFF_NO_DAD) {
-		ia->ia6_flags &= ~IN6_IFF_TENTATIVE;
-		return;
-	}
-	if (!(ifa->ifa_ifp->if_flags & IFF_UP) ||
-	    !(ifa->ifa_ifp->if_drv_flags & IFF_DRV_RUNNING) ||
-	    (ND_IFINFO(ifa->ifa_ifp)->flags & ND6_IFF_IFDISABLED)) {
-		ia->ia6_flags |= IN6_IFF_TENTATIVE;
-		return;
-	}
+
 	if ((dp = nd6_dad_find(ifa, NULL)) != NULL) {
 		/*
 		 * DAD is already in progress.  Let the existing entry
@@ -1329,11 +1315,10 @@ nd6_dad_timer(struct dadq *dp)
 	struct in6_ifaddr *ia = (struct in6_ifaddr *)ifa;
 	char ip6buf[INET6_ADDRSTRLEN];
 
-	/* Sanity check */
-	if (ia == NULL) {
-		log(LOG_ERR, "nd6_dad_timer: called with null parameter\n");
-		goto err;
-	}
+	KASSERT(ia != NULL, ("DAD entry %p with no address", dp));
+	KASSERT((ia->ia6_flags & IN6_IFF_TENTATIVE) != 0,
+	    ("DAD entry %p for non-tentative address", dp));
+
 	if (ND_IFINFO(ifp)->flags & ND6_IFF_IFDISABLED) {
 		/* Do not need DAD for ifdisabled interface. */
 		log(LOG_ERR, "nd6_dad_timer: cancel DAD on %s because of "
@@ -1347,13 +1332,6 @@ nd6_dad_timer(struct dadq *dp)
 			ifa->ifa_ifp ? if_name(ifa->ifa_ifp) : "???");
 		goto err;
 	}
-	if ((ia->ia6_flags & IN6_IFF_TENTATIVE) == 0) {
-		log(LOG_ERR, "nd6_dad_timer: called with non-tentative address "
-			"%s(%s)\n",
-			ip6_sprintf(ip6buf, &ia->ia_addr.sin6_addr),
-			ifa->ifa_ifp ? if_name(ifa->ifa_ifp) : "???");
-		goto err;
-	}
 
 	/* Stop DAD if the interface is down even after dad_maxtry attempts. */
 	if ((dp->dad_ns_tcount > V_dad_maxtry) &&