diff --git a/cylc/flow/config.py b/cylc/flow/config.py
index 1e763a65bc..d2e5fbae76 100644
--- a/cylc/flow/config.py
+++ b/cylc/flow/config.py
@@ -2258,7 +2258,6 @@ def load_graph(self):
                 task_output_opt=task_output_opt
             )
             parser.parse_graph(graph)
-            self.check_outputs(parser.task_output_opt.keys())
             task_output_opt.update(parser.task_output_opt)
             self.workflow_polling_tasks.update(
                 parser.workflow_state_polling_tasks)
@@ -2285,11 +2284,10 @@ def check_outputs(self, tasks_and_ouputs):
         safe
         """
         for task, output in tasks_and_ouputs:
-
             try:
                 registered_outputs = self.cfg['runtime'][task]['outputs']
             except KeyError:
-                pass
+                registered_outputs = []
             if (
                 not TaskOutputs.is_valid_std_name(output)
                 and output not in registered_outputs
diff --git a/tests/integration/test_optional_outputs.py b/tests/integration/test_optional_outputs.py
index da4ff989b3..8fb08784ae 100644
--- a/tests/integration/test_optional_outputs.py
+++ b/tests/integration/test_optional_outputs.py
@@ -288,14 +288,11 @@ def implicit_completion_config(mod_flow, mod_validate):
         },
         'runtime': {
             'root': {
-                'outputs': {
-                    'x': 'xxx',
-                    'y': 'yyy',
-                    'z': 'zzz',
-                }
+                'outputs': {n: f'{n}{n}{n}' for n in 'abcdefghijklxyz'}
             }
         }
     })
+
     return mod_validate(id_)
 
 
@@ -322,6 +319,7 @@ async def test_implicit_completion_expression(
     implicit_completion_config,
     task,
     condition,
+    monkeypatch,
 ):
     """It should generate a completion expression from the graph.
 
@@ -329,6 +327,7 @@ async def test_implicit_completion_expression(
     should auto generate one inferring whether outputs are required or not from
     the graph.
     """
+    # monkeypatch.setattr('cylc.flow.config.WorkflowConfig.check_outputs', lambda *_: None)
     completion_expression = get_completion_expression(
         implicit_completion_config.taskdefs[task]
     )