diff --git a/emmet-core/emmet/core/tasks.py b/emmet-core/emmet/core/tasks.py
index b7f08a8b5d..35d6ac5a68 100644
--- a/emmet-core/emmet/core/tasks.py
+++ b/emmet-core/emmet/core/tasks.py
@@ -1,6 +1,6 @@
 from datetime import datetime
 from enum import Enum
-from typing import List, Dict
+from typing import List, Dict, Union
 
 from emmet.core.vasp.task_valid import TaskState
 
@@ -144,7 +144,7 @@ class TaskDoc(BaseModel):
     Calculation-level details about VASP calculations that power Materials Project.
     """
 
-    tags: List[str] = Field(
+    tags: Union[List[str], None] = Field(
         [], title="tag", description="Metadata tagged to a given task."
     )
 
diff --git a/emmet-core/emmet/core/vasp/task_valid.py b/emmet-core/emmet/core/vasp/task_valid.py
index b875f9bf78..ae8f66aa2e 100644
--- a/emmet-core/emmet/core/vasp/task_valid.py
+++ b/emmet-core/emmet/core/vasp/task_valid.py
@@ -34,7 +34,9 @@ class BaseTaskDocument(EmmetBaseModel):
         description="Timestamp for this task document was last updateed",
     )
 
-    tags: List[str] = Field([], description="Metadata tags for this task document")
+    tags: Union[List[str], None] = Field(
+        [], description="Metadata tags for this task document"
+    )
 
     warnings: List[str] = Field(
         None, description="Any warnings related to this property"