diff --git a/src/wormhole_mailbox_server/database.py b/src/wormhole_mailbox_server/database.py
index 1db7d4e..fa99b75 100644
--- a/src/wormhole_mailbox_server/database.py
+++ b/src/wormhole_mailbox_server/database.py
@@ -14,9 +14,12 @@ def get_schema(name, version):
     return schema_bytes.decode("utf-8")
 
 def get_upgrader(name, new_version):
-    schema_bytes = resource_string("wormhole_mailbox_server",
-                                   "db-schemas/upgrade-%s-to-v%d.sql" %
-                                   (name, new_version))
+    try:
+        schema_bytes = resource_string("wormhole_mailbox_server",
+                                       "db-schemas/upgrade-%s-to-v%d.sql" %
+                                       (name, new_version))
+    except FileNotFoundError:
+        raise ValueError("no upgrader for %d" % new_version)
     return schema_bytes.decode("utf-8")
 
 CHANNELDB_TARGET_VERSION = 1
diff --git a/src/wormhole_mailbox_server/test/test_database.py b/src/wormhole_mailbox_server/test/test_database.py
index 52adeeb..bfe9440 100644
--- a/src/wormhole_mailbox_server/test/test_database.py
+++ b/src/wormhole_mailbox_server/test/test_database.py
@@ -91,6 +91,24 @@ def test_upgrade(self):
         # debug with "diff -u _trial_temp/up.sql _trial_temp/new.sql"
         self.assertEqual(dbA_text, latest_text)
 
+    def test_upgrade_fails(self):
+        basedir = self.mktemp()
+        os.mkdir(basedir)
+        fn = os.path.join(basedir, "upgrade.db")
+        self.assertNotEqual(USAGEDB_TARGET_VERSION, 1)
+
+        # create an old-version DB in a file
+        db = _get_db(fn, "usage", 1)
+        rows = db.execute("SELECT * FROM version").fetchall()
+        self.assertEqual(len(rows), 1)
+        self.assertEqual(rows[0]["version"], 1)
+        del db
+
+        # then upgrade the file to a too-new version, for which we have no
+        # upgrader
+        with self.assertRaises(DBError):
+            _get_db(fn, "usage", USAGEDB_TARGET_VERSION+1)
+
 class CreateChannel(unittest.TestCase):
     def test_memory(self):
         db = database.create_channel_db(":memory:")
diff --git a/src/wormhole_mailbox_server/test/test_web.py b/src/wormhole_mailbox_server/test/test_web.py
index 6398091..a5dbc10 100644
--- a/src/wormhole_mailbox_server/test/test_web.py
+++ b/src/wormhole_mailbox_server/test/test_web.py
@@ -7,6 +7,7 @@
 from twisted.internet.defer import inlineCallbacks, returnValue
 from ..web import make_web_server
 from ..server import SidedMessage
+from ..database import create_or_upgrade_usage_db
 from .common import ServerBase, _Util
 from .ws_client import WSFactory
 
@@ -90,8 +91,10 @@ class WebSocketAPI(_Util, ServerBase, unittest.TestCase):
     def setUp(self):
         self._lp = None
         self._clients = []
+        self._usage_db = usage_db = create_or_upgrade_usage_db(":memory:")
         yield self._setup_relay(do_listen=True,
-                            advertise_version="advertised.version")
+                                advertise_version="advertised.version",
+                                usage_db=usage_db)
 
     def tearDown(self):
         for c in self._clients:
@@ -158,6 +161,36 @@ def test_bind(self):
         self.assertEqual(err["type"], "error")
         self.assertEqual(err["error"], "ping requires 'ping'")
 
+    @inlineCallbacks
+    def test_bind_with_client_version(self):
+        c1 = yield self.make_client()
+        yield c1.next_non_ack()
+
+        c1.send("bind", appid="appid", side="side",
+                client_version=("python", "1.2.3"))
+        yield c1.sync()
+        self.assertEqual(list(self._server._apps.keys()), ["appid"])
+        v = self._usage_db.execute("SELECT * FROM `client_versions`").fetchall()
+        self.assertEqual(v[0]["app_id"], "appid")
+        self.assertEqual(v[0]["side"], "side")
+        self.assertEqual(v[0]["implementation"], "python")
+        self.assertEqual(v[0]["version"], "1.2.3")
+
+    @inlineCallbacks
+    def test_bind_with_client_version_extra_junk(self):
+        c1 = yield self.make_client()
+        yield c1.next_non_ack()
+
+        c1.send("bind", appid="appid", side="side",
+                client_version=("python", "1.2.3", "extra ignore me"))
+        yield c1.sync()
+        self.assertEqual(list(self._server._apps.keys()), ["appid"])
+        v = self._usage_db.execute("SELECT * FROM `client_versions`").fetchall()
+        self.assertEqual(v[0]["app_id"], "appid")
+        self.assertEqual(v[0]["side"], "side")
+        self.assertEqual(v[0]["implementation"], "python")
+        self.assertEqual(v[0]["version"], "1.2.3")
+
     @inlineCallbacks
     def test_list(self):
         c1 = yield self.make_client()