diff --git a/block.c b/block.c
index 8416376c9b..6dbcb7e083 100644
--- a/block.c
+++ b/block.c
@@ -6809,8 +6809,11 @@ void bdrv_refresh_filename(BlockDriverState *bs)
         pstrcpy(bs->filename, sizeof(bs->filename), bs->exact_filename);
     } else {
         QString *json = qobject_to_json(QOBJECT(bs->full_open_options));
-        snprintf(bs->filename, sizeof(bs->filename), "json:%s",
-                 qstring_get_str(json));
+        if (snprintf(bs->filename, sizeof(bs->filename), "json:%s",
+                     qstring_get_str(json)) >= sizeof(bs->filename)) {
+            /* Give user a hint if we truncated things. */
+            strcpy(bs->filename + sizeof(bs->filename) - 4, "...");
+        }
         qobject_unref(json);
     }
 }
diff --git a/block/nbd.c b/block/nbd.c
index 4ac23c8f62..eed160c5cd 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -1984,6 +1984,7 @@ static void nbd_refresh_filename(BlockDriverState *bs)
 {
     BDRVNBDState *s = bs->opaque;
     const char *host = NULL, *port = NULL, *path = NULL;
+    size_t len = 0;
 
     if (s->saddr->type == SOCKET_ADDRESS_TYPE_INET) {
         const InetSocketAddress *inet = &s->saddr->u.inet;
@@ -1996,17 +1997,21 @@ static void nbd_refresh_filename(BlockDriverState *bs)
     } /* else can't represent as pseudo-filename */
 
     if (path && s->export) {
-        snprintf(bs->exact_filename, sizeof(bs->exact_filename),
-                 "nbd+unix:///%s?socket=%s", s->export, path);
+        len = snprintf(bs->exact_filename, sizeof(bs->exact_filename),
+                       "nbd+unix:///%s?socket=%s", s->export, path);
     } else if (path && !s->export) {
-        snprintf(bs->exact_filename, sizeof(bs->exact_filename),
-                 "nbd+unix://?socket=%s", path);
+        len = snprintf(bs->exact_filename, sizeof(bs->exact_filename),
+                       "nbd+unix://?socket=%s", path);
     } else if (host && s->export) {
-        snprintf(bs->exact_filename, sizeof(bs->exact_filename),
-                 "nbd://%s:%s/%s", host, port, s->export);
+        len = snprintf(bs->exact_filename, sizeof(bs->exact_filename),
+                       "nbd://%s:%s/%s", host, port, s->export);
     } else if (host && !s->export) {
-        snprintf(bs->exact_filename, sizeof(bs->exact_filename),
-                 "nbd://%s:%s", host, port);
+        len = snprintf(bs->exact_filename, sizeof(bs->exact_filename),
+                       "nbd://%s:%s", host, port);
+    }
+    if (len > sizeof(bs->exact_filename)) {
+        /* Name is too long to represent exactly, so leave it empty. */
+        bs->exact_filename[0] = '\0';
     }
 }
 
diff --git a/nbd/server.c b/nbd/server.c
index 02b1ed0801..20754e9ebc 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -217,7 +217,7 @@ nbd_negotiate_send_rep_verr(NBDClient *client, uint32_t type,
 
     msg = g_strdup_vprintf(fmt, va);
     len = strlen(msg);
-    assert(len < 4096);
+    assert(len < NBD_MAX_STRING_SIZE);
     trace_nbd_negotiate_send_rep_err(msg);
     ret = nbd_negotiate_send_rep_len(client, type, len, errp);
     if (ret < 0) {
@@ -231,6 +231,19 @@ nbd_negotiate_send_rep_verr(NBDClient *client, uint32_t type,
     return 0;
 }
 
+/*
+ * Return a malloc'd copy of @name suitable for use in an error reply.
+ */
+static char *
+nbd_sanitize_name(const char *name)
+{
+    if (strnlen(name, 80) < 80) {
+        return g_strdup(name);
+    }
+    /* XXX Should we also try to sanitize any control characters? */
+    return g_strdup_printf("%.80s...", name);
+}
+
 /* Send an error reply.
  * Return -errno on error, 0 on success. */
 static int GCC_FMT_ATTR(4, 5)
@@ -595,9 +608,11 @@ static int nbd_negotiate_handle_info(NBDClient *client, Error **errp)
 
     exp = nbd_export_find(name);
     if (!exp) {
+        g_autofree char *sane_name = nbd_sanitize_name(name);
+
         return nbd_negotiate_send_rep_err(client, NBD_REP_ERR_UNKNOWN,
                                           errp, "export '%s' not present",
-                                          name);
+                                          sane_name);
     }
 
     /* Don't bother sending NBD_INFO_NAME unless client requested it */
@@ -995,8 +1010,10 @@ static int nbd_negotiate_meta_queries(NBDClient *client,
 
     meta->exp = nbd_export_find(export_name);
     if (meta->exp == NULL) {
+        g_autofree char *sane_name = nbd_sanitize_name(export_name);
+
         return nbd_opt_drop(client, NBD_REP_ERR_UNKNOWN, errp,
-                            "export '%s' not present", export_name);
+                            "export '%s' not present", sane_name);
     }
 
     ret = nbd_opt_read(client, &nb_queries, sizeof(nb_queries), errp);
diff --git a/tests/qemu-iotests/143 b/tests/qemu-iotests/143
index f649b36195..d2349903b1 100755
--- a/tests/qemu-iotests/143
+++ b/tests/qemu-iotests/143
@@ -58,6 +58,10 @@ _send_qemu_cmd $QEMU_HANDLE \
 $QEMU_IO_PROG -f raw -c quit \
     "nbd+unix:///no_such_export?socket=$SOCK_DIR/nbd" 2>&1 \
     | _filter_qemu_io | _filter_nbd
+# Likewise, with longest possible name permitted in NBD protocol
+$QEMU_IO_PROG -f raw -c quit \
+    "nbd+unix:///$(printf %4096d 1 | tr ' ' a)?socket=$SOCK_DIR/nbd" 2>&1 \
+    | _filter_qemu_io | _filter_nbd | sed 's/aaaa*aa/aa--aa/'
 
 _send_qemu_cmd $QEMU_HANDLE \
     "{ 'execute': 'quit' }" \
diff --git a/tests/qemu-iotests/143.out b/tests/qemu-iotests/143.out
index 1f4001c601..fc9c0a761f 100644
--- a/tests/qemu-iotests/143.out
+++ b/tests/qemu-iotests/143.out
@@ -5,6 +5,8 @@ QA output created by 143
 {"return": {}}
 qemu-io: can't open device nbd+unix:///no_such_export?socket=SOCK_DIR/nbd: Requested export not available
 server reported: export 'no_such_export' not present
+qemu-io: can't open device nbd+unix:///aa--aa1?socket=SOCK_DIR/nbd: Requested export not available
+server reported: export 'aa--aa...' not present
 { 'execute': 'quit' }
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}}
diff --git a/tests/qemu-iotests/194 b/tests/qemu-iotests/194
index 3fad7c6c1a..da7c4265ec 100755
--- a/tests/qemu-iotests/194
+++ b/tests/qemu-iotests/194
@@ -87,4 +87,14 @@ with iotests.FilePath('source.img') as source_img_path, \
             iotests.log(dest_vm.qmp('nbd-server-stop'))
             break
 
+    iotests.log('Wait for migration completion on target...')
+    migr_events = (('MIGRATION', {'data': {'status': 'completed'}}),
+                   ('MIGRATION', {'data': {'status': 'failed'}}))
+    event = dest_vm.events_wait(migr_events)
+    iotests.log(event, filters=[iotests.filter_qmp_event])
+
+    iotests.log('Check bitmaps on source:')
     iotests.log(source_vm.qmp('query-block')['return'][0]['dirty-bitmaps'])
+
+    iotests.log('Check bitmaps on target:')
+    iotests.log(dest_vm.qmp('query-block')['return'][0]['dirty-bitmaps'])
diff --git a/tests/qemu-iotests/194.out b/tests/qemu-iotests/194.out
index dd60dcc14f..a51bdb2d4f 100644
--- a/tests/qemu-iotests/194.out
+++ b/tests/qemu-iotests/194.out
@@ -21,4 +21,9 @@ Gracefully ending the `drive-mirror` job on source...
 {"data": {"device": "mirror-job0", "len": 1073741824, "offset": 1073741824, "speed": 0, "type": "mirror"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 Stopping the NBD server on destination...
 {"return": {}}
+Wait for migration completion on target...
+{"data": {"status": "completed"}, "event": "MIGRATION", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
+Check bitmaps on source:
+[{"busy": false, "count": 0, "granularity": 65536, "name": "bitmap0", "persistent": false, "recording": true, "status": "active"}]
+Check bitmaps on target:
 [{"busy": false, "count": 0, "granularity": 65536, "name": "bitmap0", "persistent": false, "recording": true, "status": "active"}]