diff --git a/sys/src/cmd/rio/dat.h b/sys/src/cmd/rio/dat.h
index f4f7f4efa..dd7d560d5 100644
--- a/sys/src/cmd/rio/dat.h
+++ b/sys/src/cmd/rio/dat.h
@@ -285,6 +285,7 @@ struct Filsys
 		int		pid;
 		char		*user;
 		Channel	*cxfidalloc;	/* chan(Xfid*) */
+		Channel	*csyncflush;	/* chan(int) */
 		Fid		*fids[Nhash];
 };
 
@@ -357,3 +358,4 @@ int		menuing;		/* menu action is pending; waiting for window to be indicated */
 int		snarfversion;	/* updated each time it is written */
 int		messagesize;		/* negotiated in 9P version setup */
 int		shiftdown;
+int		debug;
diff --git a/sys/src/cmd/rio/fsys.c b/sys/src/cmd/rio/fsys.c
index f4fea7723..5e680ea85 100644
--- a/sys/src/cmd/rio/fsys.c
+++ b/sys/src/cmd/rio/fsys.c
@@ -18,10 +18,6 @@ char	Eoffset[] = "illegal offset";
 
 int	messagesize = 8192+IOHDRSZ;	/* good start */
 
-enum{
-	DEBUG = 0
-};
-
 Dirtab dirtab[]=
 {
 	{ ".",			QTDIR,	Qdir,			0500|DMDIR },
@@ -142,6 +138,9 @@ filsysinit(Channel *cxfidalloc)
 		close(fd);
 	}
 	fs->user = estrdup(buf);
+	fs->csyncflush = chancreate(sizeof(int), 0);
+	if(fs->csyncflush == nil)
+		error("chancreate syncflush");
 	fs->cxfidalloc = cxfidalloc;
 	pid = getpid();
 
@@ -210,7 +209,7 @@ filsysproc(void *arg)
 		x->buf = buf;
 		if(convM2S(buf, n, x) != n)
 			error("convert error in convM2S");
-		if(DEBUG)
+		if(debug)
 			fprint(2, "rio:<-%F\n", &x->Fcall);
 		if(fcall[x->type] == nil)
 			x = filsysrespond(fs, x, &t, Ebadfcall);
@@ -266,7 +265,7 @@ filsysrespond(Filsys *fs, Xfid *x, Fcall *t, char *err)
 		error("convert error in convS2M");
 	if(write(fs->sfd, x->buf, n) != n)
 		error("write error in respond");
-	if(DEBUG)
+	if(debug)
 		fprint(2, "rio:->%F\n", t);
 	free(x->buf);
 	x->buf = nil;
@@ -307,14 +306,21 @@ filsysauth(Filsys *fs, Xfid *x, Fid*)
 {
 	Fcall t;
 
-		return filsysrespond(fs, x, &t, "rio: authentication not required");
+	return filsysrespond(fs, x, &t, "rio: authentication not required");
 }
 
 static
 Xfid*
-filsysflush(Filsys*, Xfid *x, Fid*)
+filsysflush(Filsys *fs, Xfid *x, Fid*)
 {
 	sendp(x->c, xfidflush);
+
+	/*
+	 * flushes need to be replied in order. xfidflush() will
+	 * awaken us when the flush has been queued.
+	 */
+	recv(fs->csyncflush, nil);
+
 	return nil;
 }
 
diff --git a/sys/src/cmd/rio/rio.c b/sys/src/cmd/rio/rio.c
index c65af8891..e6537283f 100644
--- a/sys/src/cmd/rio/rio.c
+++ b/sys/src/cmd/rio/rio.c
@@ -156,6 +156,11 @@ threadmain(int argc, char *argv[])
 	case 's':
 		scrolling = TRUE;
 		break;
+	case 'D':
+		debug++;
+		break;
+	default:
+		usage();
 	}ARGEND
 
 	if(getwd(buf, sizeof buf) == nil)
diff --git a/sys/src/cmd/rio/xfid.c b/sys/src/cmd/rio/xfid.c
index b505b2f06..662d686cf 100644
--- a/sys/src/cmd/rio/xfid.c
+++ b/sys/src/cmd/rio/xfid.c
@@ -124,24 +124,44 @@ xfidflush(Xfid *x)
 
 	for(xf=xfid; xf; xf=xf->next)
 		if(xf->flushtag == x->oldtag){
-			xf->flushtag = -1;
-			xf->flushing = TRUE;
 			incref(xf);	/* to hold data structures up at tail of synchronization */
 			if(xf->ref == 1)
 				error("ref 1 in flush");
-			if(canqlock(&xf->active)){
-				qunlock(&xf->active);
-				sendul(xf->flushc, 0);
-			}else{
-				qlock(&xf->active);	/* wait for him to finish */
-				qunlock(&xf->active);
-			}
-			xf->flushing = FALSE;
-			if(decref(xf) == 0)
-				sendp(cxfidfree, xf);
+			/* take over flushtag so follow up flushes wait for us */
+			x->flushtag = x->oldtag;
+			xf->flushtag = -1;
 			break;
 		}
+
+	/*
+	 * wakeup filsysflush() in the filsysproc so the next
+	 * flush can come in.
+	 */
+	sendul(x->fs->csyncflush, 0);
+
+	if(xf){
+		qlock(&xf->active);
+		if(xf->buf){	/* not responded yet? */
+			xf->flushing = TRUE;
+			qunlock(&xf->active);
+			sendul(xf->flushc, 0);
+			xf->flushing = FALSE;
+		}else{
+			qunlock(&xf->active);
+		}
+		if(decref(xf) == 0)
+			sendp(cxfidfree, xf);
+	}
+
+	qlock(&x->active);
+	if(x->flushing){
+		qunlock(&x->active);
+		recv(x->flushc, nil);	/* wakeup flushing xfid */
+		filsyscancel(x);
+		return;
+	}
 	filsysrespond(x->fs, x, &t, nil);
+	qunlock(&x->active);
 }
 
 void