diff --git a/artiq/frontend/artiq_client.py b/artiq/frontend/artiq_client.py
index 8305bc787..e7035381a 100755
--- a/artiq/frontend/artiq_client.py
+++ b/artiq/frontend/artiq_client.py
@@ -82,6 +82,9 @@ def get_argparser():
         "what",
         help="select object to show: schedule/devices/parameters")
 
+    parser_scan_repository = subparsers.add_parser(
+        "scan-repository", help="rescan repository")
+
     return parser
 
 
@@ -134,6 +137,10 @@ def _action_del_parameter(remote, args):
     remote.delete(args.name)
 
 
+def _action_scan_repository(remote, args):
+    remote.scan_async()
+
+
 def _show_schedule(schedule):
     clear_screen()
     if schedule:
@@ -228,6 +235,7 @@ def main():
             "del_device": "master_ddb",
             "set_parameter": "master_pdb",
             "del_parameter": "master_pdb",
+            "scan_repository": "master_repository"
         }[action]
         remote = Client(args.server, port, target_name)
         try:
diff --git a/artiq/frontend/artiq_master.py b/artiq/frontend/artiq_master.py
index bf3b6d0c5..196d4643c 100755
--- a/artiq/frontend/artiq_master.py
+++ b/artiq/frontend/artiq_master.py
@@ -56,18 +56,19 @@ def main():
     scheduler.start()
     atexit.register(lambda: loop.run_until_complete(scheduler.stop()))
 
+    repository = Repository()
+    repository.scan_async()
+
     server_control = Server({
         "master_ddb": ddb,
         "master_pdb": pdb,
         "master_schedule": scheduler,
+        "master_repository": repository
     })
     loop.run_until_complete(server_control.start(
         args.bind, args.port_control))
     atexit.register(lambda: loop.run_until_complete(server_control.stop()))
 
-    repository = Repository()
-    loop.run_until_complete(repository.scan())
-
     server_notify = Publisher({
         "schedule": scheduler.notifier,
         "devices": ddb.data,
diff --git a/artiq/master/repository.py b/artiq/master/repository.py
index c4c098f2b..3e5e2a783 100644
--- a/artiq/master/repository.py
+++ b/artiq/master/repository.py
@@ -54,8 +54,16 @@ def _sync_explist(target, source):
 class Repository:
     def __init__(self):
         self.explist = Notifier(dict())
+        self._scanning = False
 
     @asyncio.coroutine
     def scan(self):
+        if self._scanning:
+            return
+        self._scanning = True
         new_explist = yield from _scan_experiments()
         _sync_explist(self.explist, new_explist)
+        self._scanning = False
+
+    def scan_async(self):
+        asyncio.async(self.scan())