diff --git a/heat/engine/resources/openstack/mistral/external_resource.py b/heat/engine/resources/openstack/mistral/external_resource.py
index 58142c5816..9e8f1b70e3 100644
--- a/heat/engine/resources/openstack/mistral/external_resource.py
+++ b/heat/engine/resources/openstack/mistral/external_resource.py
@@ -166,7 +166,7 @@ class MistralExternalResource(resource.Resource):
 
         if execution.state in ('ERROR', 'CANCELLED'):
             raise exception.ResourceFailure(
-                exception_or_error=execution.state,
+                exception_or_error=execution.state_info,
                 resource=self,
                 action=action)