diff --git a/biscuit/apps/chronos/templates/chronos/tt_lesson.html b/biscuit/apps/chronos/templates/chronos/tt_lesson.html
index c138e3f43b084a0bd6b880a380e56fc4b4034bae..cf2c15b584b7c16c49db960d3c8a39f0f3a0c3c3 100644
--- a/biscuit/apps/chronos/templates/chronos/tt_lesson.html
+++ b/biscuit/apps/chronos/templates/chronos/tt_lesson.html
@@ -4,7 +4,7 @@
   {% if lesson_period.get_substitution.cancelled %}
     border border-danger chronos-lesson-cancelled
   {% elif lesson_period.get_substitution %}
-   border border-warning
+    border border-warning
   {% endif %}
   "
   style="