diff --git a/aredis_om/model/model.py b/aredis_om/model/model.py
index e3533294..d4e63da9 100644
--- a/aredis_om/model/model.py
+++ b/aredis_om/model/model.py
@@ -1291,6 +1291,8 @@ async def save(self, pipeline: Optional[Pipeline] = None) -> "HashModel":
             db = pipeline
         document = jsonable_encoder(self.dict())
         # TODO: Wrap any Redis response errors in a custom exception?
+        # store null values as string zero: "0"
+        document = {key: val if val else "0" for key, val in document.items()}
         await db.hset(self.key(), mapping=document)
         return self