Index: sys/net/if.c
===================================================================
--- sys/net/if.c
+++ sys/net/if.c
@@ -1309,6 +1309,10 @@
 	if (ifp->if_reassign != NULL)
 		ifp->if_reassign(ifp, new_vnet, NULL);
 
+	/* Don't re-attach DYING interfaces. */
+	if (ifp->if_flags & IFF_DYING)
+		return;
+
 	/*
 	 * Switch to the context of the target vnet.
 	 */