diff --git a/src/allmydata/scripts/tahoe_run.py b/src/allmydata/scripts/tahoe_run.py
index 7722fef51..6dfa726a3 100644
--- a/src/allmydata/scripts/tahoe_run.py
+++ b/src/allmydata/scripts/tahoe_run.py
@@ -267,7 +267,7 @@ def run(reactor, config, runApp=twistd.runApp):
     try:
         check_pid_process(pidfile)
     except (ProcessInTheWay, InvalidPidFile) as e:
-        print("ERROR: {}".format(e))
+        print("ERROR: {}".format(e), file=err)
         return 1
     else:
         reactor.addSystemEventTrigger(
diff --git a/src/allmydata/test/cli/test_run.py b/src/allmydata/test/cli/test_run.py
index ae869e475..6358b70dd 100644
--- a/src/allmydata/test/cli/test_run.py
+++ b/src/allmydata/test/cli/test_run.py
@@ -168,8 +168,10 @@ class RunTests(SyncTestCase):
         config['basedir'] = basedir.path
         config.twistd_args = []
 
+        from twisted.internet import reactor
+
         runs = []
-        result_code = run(config, runApp=runs.append)
+        result_code = run(reactor, config, runApp=runs.append)
         self.assertThat(
             config.stderr.getvalue(),
             Contains("found invalid PID file in"),
diff --git a/src/allmydata/test/common_util.py b/src/allmydata/test/common_util.py
index e63c3eef8..b6d352ab1 100644
--- a/src/allmydata/test/common_util.py
+++ b/src/allmydata/test/common_util.py
@@ -145,6 +145,7 @@ def run_cli_native(verb, *args, **kwargs):
     )
     d.addCallback(
         runner.dispatch,
+        reactor,
         stdin=stdin,
         stdout=stdout,
         stderr=stderr,