diff --git a/app/templates/monthly_overview/fragments/list.html b/app/templates/monthly_overview/fragments/list.html
index 76d0040..b618139 100644
--- a/app/templates/monthly_overview/fragments/list.html
+++ b/app/templates/monthly_overview/fragments/list.html
@@ -10,6 +10,7 @@
            role="button"
            data-bs-toggle="collapse"
            data-bs-target="#{{ x.grouper|slugify }}"
+           id="#{{ x.grouper|slugify }}-collapsible"
            aria-expanded="true"
            aria-controls="collapseExample">
         {{ x.grouper }}