diff --git a/cylc/flow/scheduler_cli.py b/cylc/flow/scheduler_cli.py
index d97ca81c459..cdf249ffa38 100644
--- a/cylc/flow/scheduler_cli.py
+++ b/cylc/flow/scheduler_cli.py
@@ -523,6 +523,7 @@ def _version_check(
                     process=str.lower,
                 )
             # we are in non-interactive mode, abort abort abort
+            print('Use "--upgrade" to upgrade the workflow.', file=sys.stderr)
             return False
         elif itt > 2 and this > that:
             # restart would INCREASE the Cylc version in a little way