diff --git a/app/api/schema/sessions.py b/app/api/schema/sessions.py
index 11b4d280ad..80cad8db3c 100644
--- a/app/api/schema/sessions.py
+++ b/app/api/schema/sessions.py
@@ -96,7 +96,7 @@ def validate_fields(self, data, original_data):
     signup_url = fields.Url(allow_none=True)
     state = fields.Str(
         validate=validate.OneOf(
-            choices=["pending", "accepted", "confirmed", "rejected", "draft"]
+            choices=["pending", "accepted", "confirmed", "rejected", "draft", "cancelled", "withdrawn"]
         ),
         allow_none=True,
         missing='draft',