diff --git a/calendar/templates/default/app.css b/calendar/templates/default/app.css
index 7d15eab849..b89d098063 100644
--- a/calendar/templates/default/app.css
+++ b/calendar/templates/default/app.css
@@ -433,6 +433,10 @@ e.g. the div with class calendar_calTimeGrid is generated by the timeGridWidget
  * User has not accepted the invitation
  */
 .calendar_calEventUnknown {
+	border-color: white;
+}
+.calendar_calEventUnknown .calendar_calEventBody,
+.calendar_calEventUnknown .calendar_calEventBodySmall {
 	background-color: white !important;
 }
 /**