diff --git a/nova/availability_zones.py b/nova/availability_zones.py
index 625ee1ff4f99..7c8d94890c4e 100644
--- a/nova/availability_zones.py
+++ b/nova/availability_zones.py
@@ -164,7 +164,7 @@ def get_availability_zones(context, get_only_available=False,
 
 def get_instance_availability_zone(context, instance):
     """Return availability zone of specified instance."""
-    host = instance.get('host')
+    host = instance.host if 'host' in instance else None
     if not host:
         # Likely hasn't reached a viable compute node yet so give back the
         # desired availability_zone in the instance record if the boot request
diff --git a/nova/tests/unit/test_availability_zones.py b/nova/tests/unit/test_availability_zones.py
index f93d3d3283fc..eb2614b7d8cb 100644
--- a/nova/tests/unit/test_availability_zones.py
+++ b/nova/tests/unit/test_availability_zones.py
@@ -267,12 +267,28 @@ class AvailabilityZoneTestCases(test.TestCase):
             az.get_instance_availability_zone(self.context, fake_inst))
 
     def test_get_instance_availability_zone_no_host(self):
-        """Test get availability zone from instance if host not set."""
+        """Test get availability zone from instance if host is None."""
         fake_inst = objects.Instance(host=None, availability_zone='inst-az')
 
         result = az.get_instance_availability_zone(self.context, fake_inst)
         self.assertEqual('inst-az', result)
 
+    def test_get_instance_availability_zone_no_host_set(self):
+        """Test get availability zone from instance if host not set.
+
+        This is testing the case in the compute API where the Instance object
+        does not have the host attribute set because it's just the object that
+        goes into the BuildRequest, it wasn't actually pulled from the DB. The
+        instance in this case doesn't actually get inserted into the DB until
+        it reaches conductor. So the host attribute may not be set but we
+        expect availability_zone always will in the API because of
+        _validate_and_build_base_options setting a default value which goes
+        into the object.
+        """
+        fake_inst = objects.Instance(availability_zone='inst-az')
+        result = az.get_instance_availability_zone(self.context, fake_inst)
+        self.assertEqual('inst-az', result)
+
     def test_get_instance_availability_zone_no_host_no_az(self):
         """Test get availability zone if neither host nor az is set."""
         fake_inst = objects.Instance(host=None, availability_zone=None)