diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9fe504aec9c..03ac454bba2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@
 
 ### Bug fixes and improvements
 
+- server: fix subscriptions with session argument in user-defined function (fix #6657)
 - server: MSSQL: Support ORDER BY for text/ntext types.
 - server: MSSQL: Support _lt, _eq, etc. for text/ntext types.
 - server: MSSQL: Fix offset when there's no order by.
diff --git a/server/src-lib/Hasura/Backends/Postgres/Execute/LiveQuery.hs b/server/src-lib/Hasura/Backends/Postgres/Execute/LiveQuery.hs
index da4125038ee..cb350a8cfbb 100644
--- a/server/src-lib/Hasura/Backends/Postgres/Execute/LiveQuery.hs
+++ b/server/src-lib/Hasura/Backends/Postgres/Execute/LiveQuery.hs
@@ -151,8 +151,8 @@ mkMultiplexedQuery rootFields = MultiplexedQuery . Q.fromBuilder . toSQL $ S.mkS
 -- about various parameters of the query along the way.
 resolveMultiplexedValue
   :: (MonadState (QueryParametersInfo ('Postgres pgKind)) m)
-  => UnpreparedValue ('Postgres pgKind) -> m S.SQLExp
-resolveMultiplexedValue = \case
+  => SessionVariables -> UnpreparedValue ('Postgres pgKind) -> m S.SQLExp
+resolveMultiplexedValue allSessionVars = \case
   UVParameter varM colVal -> do
     varJsonPath <- case fmap PS.getName varM of
       Just varName -> do
@@ -167,7 +167,10 @@ resolveMultiplexedValue = \case
     modifying qpiReferencedSessionVariables (Set.insert sessVar)
     pure $ fromResVars ty ["session", sessionVariableToText sessVar]
   UVLiteral sqlExp -> pure sqlExp
-  UVSession -> pure $ fromResVars (CollectableTypeScalar PGJSON) ["session"]
+  UVSession -> do
+    -- if the entire session is referenced, then add all session vars in referenced vars
+    modifying qpiReferencedSessionVariables (const $ getSessionVariablesSet allSessionVars)
+    pure $ fromResVars (CollectableTypeScalar PGJSON) ["session"]
   where
     fromResVars pgType jPath = addTypeAnnotation pgType $ S.SEOpApp (S.SQLOp "#>>")
       [ S.SEQIdentifier $ S.QIdentifier (S.QualifiedIdentifier (Identifier "_subs") Nothing) (Identifier "result_vars")
diff --git a/server/src-lib/Hasura/Backends/Postgres/Instances/Execute.hs b/server/src-lib/Hasura/Backends/Postgres/Instances/Execute.hs
index 9699042c348..ab832a2e00b 100644
--- a/server/src-lib/Hasura/Backends/Postgres/Instances/Execute.hs
+++ b/server/src-lib/Hasura/Backends/Postgres/Instances/Execute.hs
@@ -272,7 +272,7 @@ pgDBSubscriptionPlan
   -> m (LiveQueryPlan ('Postgres pgKind) (MultiplexedQuery ('Postgres pgKind)))
 pgDBSubscriptionPlan userInfo _sourceName sourceConfig unpreparedAST = do
   (preparedAST, PGL.QueryParametersInfo{..}) <- flip runStateT mempty $
-    for unpreparedAST $ traverseQueryDB PGL.resolveMultiplexedValue
+    for unpreparedAST $ traverseQueryDB (PGL.resolveMultiplexedValue $ _uiSession userInfo)
   let multiplexedQuery = PGL.mkMultiplexedQuery preparedAST
       roleName = _uiRole userInfo
       parameterizedPlan = ParameterizedLiveQueryPlan roleName multiplexedQuery
diff --git a/server/tests-py/queries/subscriptions/udf_session_args/setup.yaml b/server/tests-py/queries/subscriptions/udf_session_args/setup.yaml
new file mode 100644
index 00000000000..07983181fd0
--- /dev/null
+++ b/server/tests-py/queries/subscriptions/udf_session_args/setup.yaml
@@ -0,0 +1,40 @@
+type: bulk
+args:
+
+- type: run_sql
+  args:
+    sql: |
+      CREATE TABLE profile (
+          id TEXT,
+          name TEXT
+      );
+
+      INSERT INTO profile (id, name) VALUES ('10', 'Miles'), ('42', 'Charlie');
+
+      CREATE FUNCTION me(hasura_session json)
+      RETURNS SETOF profile AS $$
+        SELECT * FROM profile
+        WHERE id = hasura_session ->> 'x-hasura-user-id'
+      $$ LANGUAGE sql STABLE;
+
+- type: track_table
+  args:
+    schema: public
+    name: profile
+
+- type: create_select_permission
+  args:
+    table: profile
+    role: user
+    permission:
+      columns: [id, name]
+      filter: {}
+
+- type: track_function
+  version: 2
+  args:
+    function:
+        name: me
+        schema: public
+    configuration:
+        session_argument: hasura_session
diff --git a/server/tests-py/queries/subscriptions/udf_session_args/teardown.yaml b/server/tests-py/queries/subscriptions/udf_session_args/teardown.yaml
new file mode 100644
index 00000000000..73516c6ef7b
--- /dev/null
+++ b/server/tests-py/queries/subscriptions/udf_session_args/teardown.yaml
@@ -0,0 +1,8 @@
+type: bulk
+args:
+- type: run_sql
+  args:
+    cascade: true
+    sql: |
+      drop function me(json) cascade;
+      drop table profile cascade;
diff --git a/server/tests-py/test_subscriptions.py b/server/tests-py/test_subscriptions.py
index f6ce301245c..e4f78d30353 100644
--- a/server/tests-py/test_subscriptions.py
+++ b/server/tests-py/test_subscriptions.py
@@ -314,3 +314,35 @@ class TestSubscriptionMultiplexing:
         sql = response['sql']
         assert isinstance(sql, str), response
         return sql
+
+
+@pytest.mark.parametrize("backend", ['mssql', 'postgres'])
+@usefixtures('per_class_tests_db_state', 'per_backend_tests', 'ws_conn_init')
+class TestSubscriptionUDFWithSessionArg:
+    """
+    Test a user-defined function which uses the entire session variables as argument
+    """
+
+    query = """
+      subscription {
+        me {
+          id
+          name
+        }
+      }
+    """
+
+    @classmethod
+    def dir(cls):
+        return 'queries/subscriptions/udf_session_args'
+
+    def test_user_defined_function_with_session_argument(self, hge_ctx, ws_client):
+        ws_client.init_as_admin()
+        headers = {'x-hasura-role': 'user', 'x-hasura-user-id': '42'}
+        if hge_ctx.hge_key is not None:
+            headers['X-Hasura-Admin-Secret'] = hge_ctx.hge_key
+        payload = {'query': self.query}
+        resp = ws_client.send_query(payload, headers=headers, timeout=15)
+        ev = next(resp)
+        assert ev['type'] == 'data', ev
+        assert ev['payload']['data'] == {'me': [{'id': '42', 'name': 'Charlie'}]}, ev['payload']['data']