diff --git a/watcher/decision_engine/model/element/node.py b/watcher/decision_engine/model/element/node.py
index 4eab1b6ac..2911aa486 100644
--- a/watcher/decision_engine/model/element/node.py
+++ b/watcher/decision_engine/model/element/node.py
@@ -74,7 +74,7 @@ class Pool(storage_resource.StorageResource):
         "free_capacity_gb": wfields.NonNegativeIntegerField(),
         "provisioned_capacity_gb": wfields.NonNegativeIntegerField(),
         "allocated_capacity_gb": wfields.NonNegativeIntegerField(),
-        "virtual_free": wfields.NonNegativeIntegerField(),
+        "virtual_free": wfields.NonNegativeIntegerField(default=0),
     }
 
     def accept(self, visitor):
diff --git a/watcher/decision_engine/model/element/storage_resource.py b/watcher/decision_engine/model/element/storage_resource.py
index e65fb0152..834c6621c 100644
--- a/watcher/decision_engine/model/element/storage_resource.py
+++ b/watcher/decision_engine/model/element/storage_resource.py
@@ -28,6 +28,6 @@ class StorageResource(base.Element):
     VERSION = '1.0'
 
     fields = {
-        "uuid": wfields.StringField(),
+        "uuid": wfields.StringField(default=""),
         "human_id": wfields.StringField(default=""),
     }