diff --git a/supabase_auth/_async/gotrue_client.py b/supabase_auth/_async/gotrue_client.py
index f4c7ba09..b4803c3f 100644
--- a/supabase_auth/_async/gotrue_client.py
+++ b/supabase_auth/_async/gotrue_client.py
@@ -822,7 +822,7 @@ async def _challenge(self, params: MFAChallengeParams) -> AuthMFAChallengeRespon
         return await self._request(
             "POST",
             f"factors/{params.get('factor_id')}/challenge",
-            body={"channel": params["channel"]},
+            body={"channel": params.get("channel")},
             jwt=session.access_token,
             xform=partial(model_validate, AuthMFAChallengeResponse),
         )
diff --git a/supabase_auth/_sync/gotrue_client.py b/supabase_auth/_sync/gotrue_client.py
index 684d0365..27fc723e 100644
--- a/supabase_auth/_sync/gotrue_client.py
+++ b/supabase_auth/_sync/gotrue_client.py
@@ -814,7 +814,7 @@ def _challenge(self, params: MFAChallengeParams) -> AuthMFAChallengeResponse:
         return self._request(
             "POST",
             f"factors/{params.get('factor_id')}/challenge",
-            body={"channel": params["channel"]},
+            body={"channel": params.get("channel")},
             jwt=session.access_token,
             xform=partial(model_validate, AuthMFAChallengeResponse),
         )