diff --git a/cylc/flow/task_pool.py b/cylc/flow/task_pool.py
index c0a4e89a0c2..a10adda7d98 100644
--- a/cylc/flow/task_pool.py
+++ b/cylc/flow/task_pool.py
@@ -88,6 +88,7 @@
     from cylc.flow.task_events_mgr import TaskEventsManager
     from cylc.flow.workflow_db_mgr import WorkflowDatabaseManager
     from cylc.flow.flow_mgr import FlowMgr, FlowNums
+    from typing_extensions import Literal
 
 
 Pool = Dict['PointBase', Dict[str, TaskProxy]]
@@ -1719,10 +1720,14 @@ def set_prereqs_and_outputs(
             # Illegal flow command opts
             return
 
-        _prereqs: List[Tokens] = [
-            Tokens(prereq, relative=True)
-            for prereq in (prereqs or [])
-        ]
+        _prereqs: 'Union[List[Tokens], Literal["all"]]'
+        if prereqs == ['all']:
+            _prereqs = 'all'
+        else:
+            _prereqs = [
+                Tokens(prereq, relative=True)
+                for prereq in (prereqs or [])
+            ]
 
         # Get matching pool tasks and future task definitions.
         itasks, future_tasks, unmatched = self.filter_task_proxies(
@@ -1786,7 +1791,7 @@ def _set_outputs_itask(
     def _set_prereqs_itask(
         self,
         itask: 'TaskProxy',
-        prereqs: List[Tokens],
+        prereqs: 'Union[List[Tokens], Literal["all"]]',
         flow_nums: Set[int],
         flow_wait: bool
     ) -> None:
@@ -1795,7 +1800,7 @@ def _set_prereqs_itask(
         Prerequisite format: "cycle/task:message" or "all".
 
         """
-        if prereqs == ["all"]:
+        if prereqs == "all":
             itask.state.set_all_satisfied()
         else:
             itask.satisfy_me(prereqs)
diff --git a/tests/integration/scripts/test_set.py b/tests/integration/scripts/test_set.py
index e364384a09a..17c1555d6b7 100644
--- a/tests/integration/scripts/test_set.py
+++ b/tests/integration/scripts/test_set.py
@@ -149,3 +149,15 @@ async def test_incomplete_detection(
     async with start(schd) as log:
         schd.pool.set_prereqs_and_outputs(['1/one'], ['failed'], None, ['1'])
     assert log_filter(log, contains='1/one did not complete')
+
+
+async def test_pre_all(flow, scheduler, run):
+    """Ensure that --pre=all is interpreted as a special case
+    and _not_ tokenized.
+    """
+    id_ = flow({'scheduling': {'graph': {'R1': 'a => z'}}})
+    schd = scheduler(id_, paused_start=False)
+    async with run(schd) as log:
+        schd.pool.set_prereqs_and_outputs(['1/z'], [], ['all'], ['all'])
+        warn_or_higher = [i for i in log.records if i.levelno > 20]
+        assert warn_or_higher == []
diff --git a/tests/integration/test_task_pool.py b/tests/integration/test_task_pool.py
index c2036d8882d..facfe1f5c5a 100644
--- a/tests/integration/test_task_pool.py
+++ b/tests/integration/test_task_pool.py
@@ -1393,8 +1393,8 @@ async def test_set_outputs_live(
             'runtime': {
                 'foo': {
                     'outputs': {
-                        'x': 'x',
-                        'y': 'y'
+                        'x': 'xylophone',
+                        'y': 'yacht'
                     }
                 }
             }
@@ -1502,8 +1502,8 @@ async def test_prereq_satisfaction(
             'runtime': {
                 'a': {
                     'outputs': {
-                        'x': 'x',
-                        'y': 'y'
+                        'x': 'xylophone',
+                        'y': 'yacht'
                     }
                 }
             }