diff --git a/superset/migrations/versions/ab9a9d86e695_deprecate_time_range_endpoints.py b/superset/migrations/versions/ab9a9d86e695_deprecate_time_range_endpoints.py
index 0ce9bd5237d8f..3f149d3ff0c2a 100644
--- a/superset/migrations/versions/ab9a9d86e695_deprecate_time_range_endpoints.py
+++ b/superset/migrations/versions/ab9a9d86e695_deprecate_time_range_endpoints.py
@@ -47,7 +47,7 @@ def upgrade():
     session = db.Session(bind=bind)
 
     for slc in session.query(Slice):
-        params = json.loads(slc.params)
+        params = json.loads(slc.params or "{}")
         params.pop("time_range_endpoints", None)
         slc.params = json.dumps(params)