diff --git a/sys/netgraph7/ng_source.c b/sys/netgraph7/ng_source.c
--- a/sys/netgraph7/ng_source.c
+++ b/sys/netgraph7/ng_source.c
@@ -280,6 +280,8 @@
 	sc->snd_queue.ifq_maxlen = 2048;	/* XXX not checked */
 	ng_callout_init(&sc->intr_ch);
 
+	NG_NODE_FORCE_WRITER(node);
+
 	return (0);
 }