diff --git a/sys/netgraph/ng_tty.c b/sys/netgraph/ng_tty.c
--- a/sys/netgraph/ng_tty.c
+++ b/sys/netgraph/ng_tty.c
@@ -489,7 +489,8 @@
 	m->m_pkthdr.len++;
 
 	/* Ship off mbuf if it's time */
-	if (sc->hotchar == -1 || c == sc->hotchar || m->m_len >= MHLEN) {
+	if (sc->hotchar == -1 || (u_char)c == sc->hotchar ||
+	    m->m_len >= MHLEN) {
 		sc->m = NULL;
 		NG_SEND_DATA_ONLY(error, sc->hook, m);	/* Will queue */
 	}