diff --git a/circle/vm/operations.py b/circle/vm/operations.py
index f195b29..0dcb474 100644
--- a/circle/vm/operations.py
+++ b/circle/vm/operations.py
@@ -137,6 +137,7 @@ class CreateDiskOperation(InstanceOperation):
         for d in self.instance.disks.all():
             devnums.remove(d.dev_num)
         disk.dev_num = devnums.pop(0)
+        disk.save()
         self.instance.disks.add(disk)
 
         if self.instance.is_running: