diff --git a/course/classes/category.php b/course/classes/category.php
index a52878ee411..a1a3ec0eab2 100644
--- a/course/classes/category.php
+++ b/course/classes/category.php
@@ -272,7 +272,7 @@ class core_course_category implements renderable, cacheable_object, IteratorAggr
         if (!$coursecat) {
             // Course category not found.
             if ($strictness == MUST_EXIST) {
-                throw new moodle_exception('unknowncategory');
+                throw new moodle_exception('unknowncategory', a: $id);
             }
             $coursecat = null;
         } else if (!$alwaysreturnhidden && !$coursecat->is_uservisible($user)) {
diff --git a/lib/pagelib.php b/lib/pagelib.php
index e2fc934c651..ed61453cab0 100644
--- a/lib/pagelib.php
+++ b/lib/pagelib.php
@@ -2178,7 +2178,7 @@ class moodle_page {
         global $DB;
         $category = $DB->get_record('course_categories', array('id' => $categoryid));
         if (!$category) {
-            throw new moodle_exception('unknowncategory');
+            throw new moodle_exception('unknowncategory', a: $categoryid);
         }
         $this->_categories[$category->id] = $category;
         $parentcategoryids = explode('/', trim($category->path, '/'));