diff --git a/neutron/tests/common/exclusive_resources/resource_allocator.py b/neutron/tests/common/exclusive_resources/resource_allocator.py
index cbc04f45e61..2bd046e0733 100644
--- a/neutron/tests/common/exclusive_resources/resource_allocator.py
+++ b/neutron/tests/common/exclusive_resources/resource_allocator.py
@@ -89,7 +89,7 @@ class ResourceAllocator(object):
     @utils.synchronized('resource_allocator', external=True, lock_path='/tmp')
     def release(self, resource):
         allocations = self._get_allocations()
-        allocations.discard(resource)
+        allocations.remove(resource)
         if allocations:
             self._write_allocations(allocations)
         else:  # Clean up the file if we're releasing the last allocation