diff --git a/lib/classes/output/activity_header.php b/lib/classes/output/activity_header.php
index 2a3f27597b0..6dc63327f8f 100644
--- a/lib/classes/output/activity_header.php
+++ b/lib/classes/output/activity_header.php
@@ -66,7 +66,8 @@ class activity_header implements \renderable, \templatable {
                 $this->title = format_string($page->activityrecord->name);
             }
 
-            if (empty($layoutoptions['nodescription']) && $page->activityrecord->intro && trim($page->activityrecord->intro)) {
+            if (empty($layoutoptions['nodescription']) && !empty($page->activityrecord->intro) &&
+                    trim($page->activityrecord->intro)) {
                 $this->description = format_module_intro($this->page->activityname, $page->activityrecord, $page->cm->id);
             }
         }