diff --git a/nova/api/ec2/ec2utils.py b/nova/api/ec2/ec2utils.py
index fdff3d9f470d..93fa522acc8c 100644
--- a/nova/api/ec2/ec2utils.py
+++ b/nova/api/ec2/ec2utils.py
@@ -129,7 +129,9 @@ def id_to_ec2_id(instance_id, template='i-%08x'):
 
 def id_to_ec2_inst_id(instance_id):
     """Get or create an ec2 instance ID (i-[base 16 number]) from uuid."""
-    if utils.is_uuid_like(instance_id):
+    if instance_id is None:
+        return None
+    elif utils.is_uuid_like(instance_id):
         ctxt = context.get_admin_context()
         int_id = get_int_id_from_instance_uuid(ctxt, instance_id)
         return id_to_ec2_id(int_id)
diff --git a/nova/tests/api/ec2/test_cloud.py b/nova/tests/api/ec2/test_cloud.py
index 234d84ec8b61..b9fab73a5ce2 100644
--- a/nova/tests/api/ec2/test_cloud.py
+++ b/nova/tests/api/ec2/test_cloud.py
@@ -312,6 +312,18 @@ class CloudTestCase(test.TestCase):
                           self.cloud.disassociate_address,
                           self.context, public_ip=address)
 
+    def test_disassociate_unassociated_address(self):
+        address = "10.10.10.10"
+        db.floating_ip_create(self.context,
+                              {'address': address,
+                               'pool': 'nova'})
+        self.cloud.allocate_address(self.context)
+        self.cloud.describe_addresses(self.context)
+        self.assertRaises(exception.InstanceNotFound,
+                          self.cloud.disassociate_address,
+                          self.context, public_ip=address)
+        db.floating_ip_destroy(self.context, address)
+
     def test_describe_security_groups(self):
         """Makes sure describe_security_groups works and filters results."""
         sec = db.security_group_create(self.context,
diff --git a/nova/tests/api/ec2/test_middleware.py b/nova/tests/api/ec2/test_middleware.py
index a618817bd18e..7f30b924e015 100644
--- a/nova/tests/api/ec2/test_middleware.py
+++ b/nova/tests/api/ec2/test_middleware.py
@@ -116,6 +116,15 @@ class ExecutorTestCase(test.TestCase):
         result = self._execute(not_found)
         self.assertIn('i-00000005', self._extract_message(result))
 
+    def test_instance_not_found_none(self):
+        def not_found(context):
+            raise exception.InstanceNotFound(instance_id=None)
+
+        # NOTE(mikal): we want no exception to be raised here, which was what
+        # was happening in bug/1080406
+        result = self._execute(not_found)
+        self.assertIn('None', self._extract_message(result))
+
     def test_snapshot_not_found(self):
         def not_found(context):
             raise exception.SnapshotNotFound(snapshot_id=5)