diff --git a/labgrid/util/helper.py b/labgrid/util/helper.py
index 93b98b050..139615640 100644
--- a/labgrid/util/helper.py
+++ b/labgrid/util/helper.py
@@ -41,8 +41,14 @@ class ProcessWrapper:
     loglevel = logging.INFO
 
     @step(args=['command'], result=True, tag='process')
-    def check_output(self, command, *, print_on_silent_log=False, input=None, stdin=None, timeout=None): # pylint: disable=redefined-builtin
+    def check_output(
+        self, command, *, print_on_silent_log=False, input=None, stdin=None, stderr=subprocess.STDOUT, timeout=None
+    ):  # pylint: disable=redefined-builtin
         """Run a command and supply the output to callback functions"""
+
+        if stderr not in (None, subprocess.STDOUT, subprocess.DEVNULL):
+            raise NotImplementedError(f"{stderr=} not supported")
+
         logger = logging.getLogger("Process")
         res = []
         mfd, sfd = pty.openpty()
@@ -59,8 +65,7 @@ def check_output(self, command, *, print_on_silent_log=False, input=None, stdin=
         elif stdin is not None:
             kwargs['stdin'] = stdin
 
-        process = subprocess.Popen(command, stderr=sfd,
-                                   stdout=sfd, bufsize=0, **kwargs)
+        process = subprocess.Popen(command, stderr=stderr, stdout=sfd, bufsize=0, **kwargs)
 
         logger.log(ProcessWrapper.loglevel, "[%d] command: %s", process.pid, " ".join(command))
 
diff --git a/tests/test_powerdriver.py b/tests/test_powerdriver.py
index 8926333c6..d7076d944 100644
--- a/tests/test_powerdriver.py
+++ b/tests/test_powerdriver.py
@@ -1,3 +1,4 @@
+import subprocess
 from urllib.parse import urlparse
 
 import pytest
@@ -81,7 +82,7 @@ def test_on(self, target, mocker):
         d.on()
 
         popen.assert_called_once_with(['set', '-1', 'foo-board'], bufsize=0,
-                                      stderr=2, stdout=2)
+                                      stderr=subprocess.STDOUT, stdout=2)
 
     def test_off(self, target, mocker):
         pty = mocker.patch('pty.openpty')
@@ -107,7 +108,7 @@ def test_off(self, target, mocker):
         d.off()
 
         popen.assert_called_once_with(['set', '-0', 'foo-board'], bufsize=0,
-                                      stderr=2, stdout=2)
+                                      stderr=subprocess.STDOUT, stdout=2)
 
     def test_cycle(self, target, mocker):
         pty = mocker.patch('pty.openpty')
@@ -135,10 +136,8 @@ def test_cycle(self, target, mocker):
         d.cycle()
 
         assert popen.call_args_list == [
-            mocker.call(['set', '-0', 'foo-board'], bufsize=0, stderr=2,
-                        stdout=2),
-            mocker.call(['set', '-1', 'foo-board'], bufsize=0, stderr=2,
-                        stdout=2),
+            mocker.call(['set', '-0', 'foo-board'], bufsize=0, stderr=subprocess.STDOUT, stdout=2),
+            mocker.call(['set', '-1', 'foo-board'], bufsize=0, stderr=subprocess.STDOUT, stdout=2),
         ]
         m_sleep.assert_called_once_with(2.0)
 
@@ -171,7 +170,7 @@ def test_cycle_explicit(self, target, mocker):
         d.cycle()
 
         popen.assert_called_once_with(['set', '-c', 'foo-board'], bufsize=0,
-                                      stderr=2, stdout=2)
+                                      stderr=subprocess.STDOUT, stdout=2)
         m_sleep.assert_not_called()
 
 class TestNetworkPowerDriver: