diff --git a/minix/servers/vfs/comm.c b/minix/servers/vfs/comm.c
index 663caebb2..9381cc323 100644
--- a/minix/servers/vfs/comm.c
+++ b/minix/servers/vfs/comm.c
@@ -114,17 +114,18 @@ int drv_sendrec(endpoint_t drv_e, message *reqmp)
 	if ((r = asynsend3(drv_e, self->w_drv_sendrec, AMF_NOREPLY)) == OK) {
 		/* Yield execution until we've received the reply */
 		worker_wait();
+
 	} else {
 		printf("VFS: drv_sendrec: error sending msg to driver %d: %d\n",
 			drv_e, r);
-		util_stacktrace();
+		self->w_drv_sendrec = NULL;
 	}
 
+	assert(self->w_drv_sendrec == NULL);
 	dp->dmap_servicing = INVALID_THREAD;
 	self->w_task = NONE;
-	self->w_drv_sendrec = NULL;
 	unlock_dmap(dp);
-	return(OK);
+	return(r);
 }
 
 /*===========================================================================*
@@ -141,6 +142,7 @@ int fs_sendrec(endpoint_t fs_e, message *reqmp)
   }
   if (fs_e == fp->fp_endpoint) return(EDEADLK);
 
+  assert(self->w_sendrec == NULL);
   self->w_sendrec = reqmp;	/* Where to store request and reply */
 
   /* Find out whether we can send right away or have to enqueue */
@@ -157,6 +159,8 @@ int fs_sendrec(endpoint_t fs_e, message *reqmp)
 
   worker_wait();	/* Yield execution until we've received the reply. */
 
+  assert(self->w_sendrec == NULL);
+
   return(reqmp->m_type);
 }
 
@@ -170,6 +174,7 @@ int vm_sendrec(message *reqmp)
   assert(self);
   assert(reqmp);
 
+  assert(self->w_sendrec == NULL);
   self->w_sendrec = reqmp;	/* Where to store request and reply */
 
   r = sendmsg(NULL, VM_PROC_NR, self);
@@ -180,6 +185,8 @@ int vm_sendrec(message *reqmp)
 
   worker_wait();	/* Yield execution until we've received the reply. */
 
+  assert(self->w_sendrec == NULL);
+
   return(reqmp->m_type);
 }
 
diff --git a/minix/servers/vfs/device.c b/minix/servers/vfs/device.c
index 53b1e9088..454f66554 100644
--- a/minix/servers/vfs/device.c
+++ b/minix/servers/vfs/device.c
@@ -445,7 +445,7 @@ static int cdev_opcl(
   worker_wait();
 
   self->w_task = NONE;
-  self->w_drv_sendrec = NULL;
+  assert(self->w_drv_sendrec == NULL);
 
   /* Process the reply. */
   r = dev_mess.m_lchardriver_vfs_reply.status;
@@ -613,7 +613,7 @@ int cdev_cancel(dev_t dev)
   worker_wait();
 
   self->w_task = NONE;
-  self->w_drv_sendrec = NULL;
+  assert(self->w_drv_sendrec == NULL);
 
   /* Clean up and return the result (note: the request may have completed). */
   if (GRANT_VALID(fp->fp_grant)) {
@@ -765,9 +765,10 @@ static void cdev_generic_reply(message *m_ptr)
   }
   rfp = &fproc[slot];
   wp = rfp->fp_worker;
-  if (wp != NULL && wp->w_task == who_e) {
+  if (wp != NULL && wp->w_task == who_e && wp->w_drv_sendrec != NULL) {
 	assert(!fp_is_blocked(rfp));
 	*wp->w_drv_sendrec = *m_ptr;
+	wp->w_drv_sendrec = NULL;
 	worker_signal(wp);	/* Continue open/close/cancel */
   } else if (rfp->fp_blocked_on != FP_BLOCKED_ON_OTHER ||
 		rfp->fp_task != m_ptr->m_source) {
@@ -840,12 +841,11 @@ void bdev_reply(void)
   }
 
   wp = worker_get(dp->dmap_servicing);
-  if (wp == NULL || wp->w_task != who_e) {
+  if (wp == NULL || wp->w_task != who_e || wp->w_drv_sendrec == NULL) {
 	printf("VFS: no worker thread waiting for a reply from %d\n", who_e);
 	return;
   }
 
-  assert(wp->w_drv_sendrec != NULL);
   *wp->w_drv_sendrec = m_in;
   wp->w_drv_sendrec = NULL;
   worker_signal(wp);
diff --git a/minix/servers/vfs/main.c b/minix/servers/vfs/main.c
index adbb85ce7..6b7eb8a68 100644
--- a/minix/servers/vfs/main.c
+++ b/minix/servers/vfs/main.c
@@ -194,8 +194,17 @@ static void do_reply(struct worker_thread *wp)
   if (wp->w_task != who_e) {
 	printf("VFS: tid %d: expected %d to reply, not %d\n",
 		wp->w_tid, wp->w_task, who_e);
+	return;
+  }
+  /* It should be impossible to trigger the following case, but it is here for
+   * consistency reasons: worker_stop() resets w_sendrec but not w_task.
+   */
+  if (wp->w_sendrec == NULL) {
+	printf("VFS: tid %d: late reply from %d ignored\n", wp->w_tid, who_e);
+	return;
   }
   *wp->w_sendrec = m_in;
+  wp->w_sendrec = NULL;
   wp->w_task = NONE;
   if(vmp) vmp->m_comm.c_cur_reqs--; /* We've got our reply, make room for others */
   worker_signal(wp); /* Continue this thread */
diff --git a/minix/servers/vfs/worker.c b/minix/servers/vfs/worker.c
index 7f01aef23..e942a5a02 100644
--- a/minix/servers/vfs/worker.c
+++ b/minix/servers/vfs/worker.c
@@ -469,8 +469,10 @@ void worker_stop(struct worker_thread *worker)
 	/* This thread is communicating with a driver or file server */
 	if (worker->w_drv_sendrec != NULL) {			/* Driver */
 		worker->w_drv_sendrec->m_type = EIO;
+		worker->w_drv_sendrec = NULL;
 	} else if (worker->w_sendrec != NULL) {		/* FS */
 		worker->w_sendrec->m_type = EIO;
+		worker->w_sendrec = NULL;
 	} else {
 		panic("reply storage consistency error");	/* Oh dear */
 	}