diff --git a/theme/boost/scss/moodle/calendar.scss b/theme/boost/scss/moodle/calendar.scss
index 97a40a04ea2..415f0f4d259 100644
--- a/theme/boost/scss/moodle/calendar.scss
+++ b/theme/boost/scss/moodle/calendar.scss
@@ -429,6 +429,7 @@ table.calendartable caption {
 
 .summary-modal-container {
     .description-content {
+        overflow-wrap: break-word;
         > p {
             margin: 0;
         }
diff --git a/theme/boost/style/moodle.css b/theme/boost/style/moodle.css
index 304ba3707a8..ff6ab2a3d27 100644
--- a/theme/boost/style/moodle.css
+++ b/theme/boost/style/moodle.css
@@ -11659,8 +11659,10 @@ table.calendartable caption {
 .day-popover-content:empty + .day-popover-alternate {
   display: block; }
 
-.summary-modal-container .description-content > p {
-  margin: 0; }
+.summary-modal-container .description-content {
+  overflow-wrap: break-word; }
+  .summary-modal-container .description-content > p {
+    margin: 0; }
 
 .summary-modal-container .location-content {
   overflow-wrap: break-word; }
diff --git a/theme/classic/style/moodle.css b/theme/classic/style/moodle.css
index 6ddf3925837..8a804509d79 100644
--- a/theme/classic/style/moodle.css
+++ b/theme/classic/style/moodle.css
@@ -11900,8 +11900,10 @@ table.calendartable caption {
 .day-popover-content:empty + .day-popover-alternate {
   display: block; }
 
-.summary-modal-container .description-content > p {
-  margin: 0; }
+.summary-modal-container .description-content {
+  overflow-wrap: break-word; }
+  .summary-modal-container .description-content > p {
+    margin: 0; }
 
 .summary-modal-container .location-content {
   overflow-wrap: break-word; }