diff --git a/docs/DEBUGGING.md b/docs/DEBUGGING.md
index 3e89a5d8a4..175e557e6c 100644
--- a/docs/DEBUGGING.md
+++ b/docs/DEBUGGING.md
@@ -93,7 +93,7 @@ systemctl enable debug-shell.service
 or by specifying
 
 ```sh
-systemd.debug-shell=1
+systemd.debug_shell=1
 ```
 
 on the kernel command line.