diff --git a/course/lib.php b/course/lib.php
index 97b16b3fa32..33978affb8c 100644
--- a/course/lib.php
+++ b/course/lib.php
@@ -1692,11 +1692,15 @@ function make_categories_list(&$list, &$parents, $requiredcapability = '',
         }
 
         // Add this category to $list, if the permissions check out.
-        if ($requiredcapability) {
-            ensure_context_subobj_present($category, CONTEXT_COURSECAT);
-        }
-        if (!$requiredcapability || has_all_capabilities($requiredcapability, $category->context)) {
+        if (empty($requiredcapability)) {
             $list[$category->id] = $path;
+
+        } else {
+            ensure_context_subobj_present($category, CONTEXT_COURSECAT);
+            $requiredcapability = (array)$requiredcapability;
+            if (has_all_capabilities($requiredcapability, $category->context)) {
+                $list[$category->id] = $path;
+            }
         }
     }
 
diff --git a/lib/accesslib.php b/lib/accesslib.php
index a94c7a550d6..71364524a84 100755
--- a/lib/accesslib.php
+++ b/lib/accesslib.php
@@ -518,6 +518,10 @@ function has_any_capability($capabilities, $context, $userid=NULL, $doanything=t
  * @return bool
  */
 function has_all_capabilities($capabilities, $context, $userid=NULL, $doanything=true) {
+    if (!is_array($capabilities)) {
+        debugging('Incorrect $capabilities parameter in has_all_capabilities() call - must be an array');
+        return false;
+    }
     foreach ($capabilities as $capability) {
         if (!has_capability($capability, $context, $userid, $doanything)) {
             return false;