diff --git a/sys/dev/sio/sio.c b/sys/dev/sio/sio.c
index e5115e8afbba..1d8bf01fee82 100644
--- a/sys/dev/sio/sio.c
+++ b/sys/dev/sio/sio.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)com.c	7.5 (Berkeley) 5/16/91
- *	$Id: sio.c,v 1.68 1995/02/26 02:30:18 bde Exp $
+ *	$Id: sio.c,v 1.69 1995/02/28 00:20:54 pst Exp $
  */
 
 #include "sio.h"
@@ -1531,12 +1531,16 @@ repeat:
 		     * Only have it in standard one now.
 		     */
 		    && linesw[tp->t_line].l_rint == ttyinput) {
+			int queue_full = 0;
+
 			if ((tp->t_iflag & IXOFF) &&
 			    tp->t_cc[VSTOP] != _POSIX_VDISABLE &&
-			    putc(tp->t_cc[VSTOP], &tp->t_outq) == 0 ||
+			    (queue_full = putc(tp->t_cc[VSTOP], &tp->t_outq)) == 0 ||
 			    (com->state & CS_RTS_IFLOW)) {
 				tp->t_state |= TS_TBLOCK;
 				ttstart(tp);
+				if (queue_full) /* try again */
+					tp->t_state &= ~TS_TBLOCK;
 			}
 		}
 		/*
diff --git a/sys/i386/isa/sio.c b/sys/i386/isa/sio.c
index e5115e8afbba..1d8bf01fee82 100644
--- a/sys/i386/isa/sio.c
+++ b/sys/i386/isa/sio.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)com.c	7.5 (Berkeley) 5/16/91
- *	$Id: sio.c,v 1.68 1995/02/26 02:30:18 bde Exp $
+ *	$Id: sio.c,v 1.69 1995/02/28 00:20:54 pst Exp $
  */
 
 #include "sio.h"
@@ -1531,12 +1531,16 @@ repeat:
 		     * Only have it in standard one now.
 		     */
 		    && linesw[tp->t_line].l_rint == ttyinput) {
+			int queue_full = 0;
+
 			if ((tp->t_iflag & IXOFF) &&
 			    tp->t_cc[VSTOP] != _POSIX_VDISABLE &&
-			    putc(tp->t_cc[VSTOP], &tp->t_outq) == 0 ||
+			    (queue_full = putc(tp->t_cc[VSTOP], &tp->t_outq)) == 0 ||
 			    (com->state & CS_RTS_IFLOW)) {
 				tp->t_state |= TS_TBLOCK;
 				ttstart(tp);
+				if (queue_full) /* try again */
+					tp->t_state &= ~TS_TBLOCK;
 			}
 		}
 		/*
diff --git a/sys/isa/sio.c b/sys/isa/sio.c
index e5115e8afbba..1d8bf01fee82 100644
--- a/sys/isa/sio.c
+++ b/sys/isa/sio.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)com.c	7.5 (Berkeley) 5/16/91
- *	$Id: sio.c,v 1.68 1995/02/26 02:30:18 bde Exp $
+ *	$Id: sio.c,v 1.69 1995/02/28 00:20:54 pst Exp $
  */
 
 #include "sio.h"
@@ -1531,12 +1531,16 @@ repeat:
 		     * Only have it in standard one now.
 		     */
 		    && linesw[tp->t_line].l_rint == ttyinput) {
+			int queue_full = 0;
+
 			if ((tp->t_iflag & IXOFF) &&
 			    tp->t_cc[VSTOP] != _POSIX_VDISABLE &&
-			    putc(tp->t_cc[VSTOP], &tp->t_outq) == 0 ||
+			    (queue_full = putc(tp->t_cc[VSTOP], &tp->t_outq)) == 0 ||
 			    (com->state & CS_RTS_IFLOW)) {
 				tp->t_state |= TS_TBLOCK;
 				ttstart(tp);
+				if (queue_full) /* try again */
+					tp->t_state &= ~TS_TBLOCK;
 			}
 		}
 		/*
diff --git a/sys/kern/tty.c b/sys/kern/tty.c
index 2020d7d30734..9edf66a39b86 100644
--- a/sys/kern/tty.c
+++ b/sys/kern/tty.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)tty.c	8.8 (Berkeley) 1/21/94
- * $Id: tty.c,v 1.33 1995/02/27 19:47:31 ugen Exp $
+ * $Id: tty.c,v 1.34 1995/02/28 00:21:03 pst Exp $
  */
 
 #include "snp.h"
@@ -1098,12 +1098,16 @@ ttyflush(tp, rw)
 	}
 	if ((rw & FREAD) &&
 	    ISSET(tp->t_state, TS_TBLOCK) && tp->t_rawq.c_cc < TTYHOG/5) {
+		int queue_full = 0;
+
 		if (ISSET(tp->t_iflag, IXOFF) &&
 		    tp->t_cc[VSTART] != _POSIX_VDISABLE &&
-		    putc(tp->t_cc[VSTART], &tp->t_outq) == 0 ||
+		    (queue_full = putc(tp->t_cc[VSTART], &tp->t_outq)) == 0 ||
 		    ISSET(tp->t_cflag, CRTS_IFLOW)) {
 			CLR(tp->t_state, TS_TBLOCK);
 			ttstart(tp);
+			if (queue_full) /* try again */
+				SET(tp->t_state, TS_TBLOCK);
 		}
 	}
 	splx(s);
@@ -1137,12 +1141,16 @@ ttyblock(tp)
 	if (total >= TTYHOG / 2 &&
 	    !ISSET(tp->t_state, TS_TBLOCK) &&
 	    (!ISSET(tp->t_lflag, ICANON) || tp->t_canq.c_cc > 0)) {
+		int queue_full = 0;
+
 		if (ISSET(tp->t_iflag, IXOFF) &&
 		    tp->t_cc[VSTOP] != _POSIX_VDISABLE &&
-		    putc(tp->t_cc[VSTOP], &tp->t_outq) == 0 ||
+		    (queue_full = putc(tp->t_cc[VSTOP], &tp->t_outq)) == 0 ||
 		    ISSET(tp->t_cflag, CRTS_IFLOW)) {
 			SET(tp->t_state, TS_TBLOCK);
 			ttstart(tp);
+			if (queue_full) /* try again */
+				CLR(tp->t_state, TS_TBLOCK);
 		}
 	}
 }
@@ -1531,12 +1539,16 @@ read:
 	 */
 	s = spltty();
 	if (ISSET(tp->t_state, TS_TBLOCK) && tp->t_rawq.c_cc < TTYHOG/5) {
+		int queue_full = 0;
+
 		if (ISSET(tp->t_iflag, IXOFF) &&
 		    cc[VSTART] != _POSIX_VDISABLE &&
-		    putc(cc[VSTART], &tp->t_outq) == 0 ||
+		    (queue_full = putc(cc[VSTART], &tp->t_outq)) == 0 ||
 		    ISSET(tp->t_cflag, CRTS_IFLOW)) {
 			CLR(tp->t_state, TS_TBLOCK);
 			ttstart(tp);
+			if (queue_full) /* try again */
+				SET(tp->t_state, TS_TBLOCK);
 		}
 	}
 	splx(s);