diff --git a/sys/dev/usb/serial/usb_serial.c b/sys/dev/usb/serial/usb_serial.c
index 2047bc3a13f..3bf6ee0702f 100644
--- a/sys/dev/usb/serial/usb_serial.c
+++ b/sys/dev/usb/serial/usb_serial.c
@@ -797,10 +797,14 @@ ucom_inwakeup(struct tty *tp)
 	DPRINTF("tp=%p\n", tp);
 
 	if (ttydisc_can_bypass(tp) != 0 || 
-	    (sc->sc_flag & UCOM_FLAG_HL_READY) == 0) {
+	    (sc->sc_flag & UCOM_FLAG_HL_READY) == 0 ||
+	    (sc->sc_flag & UCOM_FLAG_INWAKEUP) != 0) {
 		return;
 	}
 
+	/* prevent recursion */
+	sc->sc_flag |= UCOM_FLAG_INWAKEUP;
+
 	pos = sc->sc_jitterbuf_out;
 
 	while (sc->sc_jitterbuf_in != pos) {
@@ -821,6 +825,8 @@ ucom_inwakeup(struct tty *tp)
 	if ((sc->sc_jitterbuf_in == pos) && 
 	    (sc->sc_flag & UCOM_FLAG_RTS_IFLOW))
 		ucom_rts(sc, 0);
+
+	sc->sc_flag &= ~UCOM_FLAG_INWAKEUP;
 }
 
 static int
diff --git a/sys/dev/usb/serial/usb_serial.h b/sys/dev/usb/serial/usb_serial.h
index d045fbe8d31..0ac822d4ab0 100644
--- a/sys/dev/usb/serial/usb_serial.h
+++ b/sys/dev/usb/serial/usb_serial.h
@@ -183,6 +183,7 @@ struct ucom_softc {
 #define	UCOM_FLAG_CONSOLE	0x80	/* set if device is a console */
 #define	UCOM_FLAG_WAIT_REFS   0x0100	/* set if we must wait for refs */
 #define	UCOM_FLAG_FREE_UNIT   0x0200	/* set if we must free the unit */
+#define	UCOM_FLAG_INWAKEUP    0x0400	/* set if we are in the tsw_inwakeup callback */
 	uint8_t	sc_lsr;
 	uint8_t	sc_msr;
 	uint8_t	sc_mcr;