diff --git a/webservice/webservice.py b/webservice/webservice.py
index 3f99637293bd0294613767ca3e62269ff404cb96..4905d7b43efac8d52d276e54124879f68049be94 100644
--- a/webservice/webservice.py
+++ b/webservice/webservice.py
@@ -241,7 +241,7 @@ def change_config(config, updated_config, instrument,
 async def run_proc_async(cmd: List[str]) -> Tuple[Optional[int], bytes, bytes]:
     """Run a subprocess to completion using asyncio, capturing stdout
 
-    Returns the numeric exit code and stdout (bytes)
+    Returns the numeric exit code, stdout and stderr (bytes)
     """
     proc = await asyncio.create_subprocess_exec(
         *cmd, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE