diff --git a/data/helpers.d/system b/data/helpers.d/system
index 71db85390..d63a4b482 100644
--- a/data/helpers.d/system
+++ b/data/helpers.d/system
@@ -63,6 +63,9 @@ ynh_get_debian_release () {
 # | arg: -a, --action=       - Action to perform with systemctl. Default: start
 # | arg: -l, --line_match=   - Line to match - The line to find in the log to attest the service have finished to boot.
 #                              If not defined it don't wait until the service is completely started.
+#                              WARNING: When using --line_match, you should always add `ynh_clean_check_starting` into your
+#                                `ynh_clean_setup` at the beginning of the script. Otherwise, tail will not stop in case of failure
+#                                of the script. The script will then hang forever.
 # | arg: -p, --log_path=     - Log file - Path to the log file. Default : /var/log/$app/$app.log
 # | arg: -t, --timeout=      - Timeout - The maximum time to wait before ending the watching. Default : 300 seconds.
 # | arg: -e, --length=       - Length of the error log : Default : 20