diff --git a/theme/bootstrapbase/less/moodle/course.less b/theme/bootstrapbase/less/moodle/course.less
index b2b1b271647..1379e5d0b0e 100644
--- a/theme/bootstrapbase/less/moodle/course.less
+++ b/theme/bootstrapbase/less/moodle/course.less
@@ -71,6 +71,15 @@
             right: 0;
             top: 0;
         }
+
+        .activityinstance {
+            .dimmed {
+                img.activityicon {
+                  opacity: 0.5;
+                  filter: alpha(opacity=50);
+                }
+            }
+        }
     }
 
     .filler {