diff --git a/karbor/objects/operation_log.py b/karbor/objects/operation_log.py
index 4a220b22..984b70e4 100644
--- a/karbor/objects/operation_log.py
+++ b/karbor/objects/operation_log.py
@@ -29,7 +29,7 @@ class OperationLog(base.KarborPersistentObject, base.KarborObject,
     fields = {
         'id': fields.UUIDField(),
         'project_id': fields.UUIDField(),
-        'operation_type': fields.UUIDField(),
+        'operation_type': fields.StringField(),
         'checkpoint_id': fields.UUIDField(nullable=True),
         'plan_id': fields.UUIDField(nullable=True),
         'provider_id': fields.UUIDField(nullable=True),