diff --git a/gns3server/controller/project.py b/gns3server/controller/project.py
index 8796e028f..5bf237442 100644
--- a/gns3server/controller/project.py
+++ b/gns3server/controller/project.py
@@ -536,7 +536,7 @@ def delete_snapshot(self, snapshot_id):
     @asyncio.coroutine
     def close(self, ignore_notification=False):
         yield from self.stop_all()
-        for compute in self._project_created_on_compute:
+        for compute in list(self._project_created_on_compute):
             try:
                 yield from compute.post("/projects/{}/close".format(self._id), dont_connect=True)
             # We don't care if a compute is down at this step