diff --git a/data/hooks/diagnosis/80-apps.py b/data/hooks/diagnosis/80-apps.py
index a75193a45..5aec48ed8 100644
--- a/data/hooks/diagnosis/80-apps.py
+++ b/data/hooks/diagnosis/80-apps.py
@@ -76,7 +76,7 @@ class AppDiagnoser(Diagnoser):
         for deprecated_helper in deprecated_helpers:
             if (
                 os.system(
-                    f"grep -hr '{deprecated_helper}' {app['setting_path']}/scripts/ | grep -v -q '^\s*#'"
+                    f"grep -hr '{deprecated_helper}' {app['setting_path']}/scripts/ | grep -v -q '^\\s*#'"
                 )
                 == 0
             ):
diff --git a/tox.ini b/tox.ini
index 733a0613d..267134e57 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,7 +9,7 @@ deps =
   py37-mypy: mypy >= 0.900
 commands =
         py37-lint: flake8 src doc data tests --ignore E402,E501,E203,W503 --exclude src/yunohost/vendor
-        py37-invalidcode: flake8 src data --exclude src/yunohost/tests,src/yunohost/vendor --select F,E722
+        py37-invalidcode: flake8 src data --exclude src/yunohost/tests,src/yunohost/vendor --select F,E722,W605
         py37-black-check: black --check --diff src doc data tests
         py37-black-run: black src doc data tests
         py37-mypy: mypy  --ignore-missing-import --install-types --non-interactive --follow-imports silent src/yunohost/ --exclude (acme_tiny|data_migrations)