diff --git a/gns3server/handlers/api/version_handler.py b/gns3server/handlers/api/version_handler.py
index af01fe14..930c733e 100644
--- a/gns3server/handlers/api/version_handler.py
+++ b/gns3server/handlers/api/version_handler.py
@@ -47,12 +47,3 @@ class VersionHandler:
         if request.json["version"] != __version__:
             raise HTTPConflict(text="Client version {} differs with server version {}".format(request.json["version"], __version__))
         response.json({"version": __version__})
-
-    @staticmethod
-    @Route.get(
-        r"/sleep/{vm_id}",
-        description="Retrieve the server version number",
-        output=VERSION_SCHEMA)
-    def sleep(request, response):
-        yield from asyncio.sleep(1)
-        response.json({"version": __version__})
diff --git a/gns3server/web/route.py b/gns3server/web/route.py
index 8afaae20..bf30e35f 100644
--- a/gns3server/web/route.py
+++ b/gns3server/web/route.py
@@ -163,9 +163,16 @@ class Route(object):
                     vm_id = request.match_info.get("vm_id")
                     if vm_id is None:
                         vm_id = request.match_info["device_id"]
-                    cls._vm_locks.setdefault(vm_id, asyncio.Lock())
-                    with (yield from cls._vm_locks[vm_id]):
+                    cls._vm_locks.setdefault(vm_id, {"lock": asyncio.Lock(), "concurrency": 0})
+                    cls._vm_locks[vm_id]["concurrency"] += 1
+
+                    with (yield from cls._vm_locks[vm_id]["lock"]):
                         response = yield from control_schema(request)
+                    cls._vm_locks[vm_id]["concurrency"] -= 1
+
+                    # No more waiting requests, garbage collect the lock
+                    if cls._vm_locks[vm_id]["concurrency"] <= 0:
+                        del cls._vm_locks[vm_id]
                 else:
                     response = yield from control_schema(request)
                 return response