diff --git a/lib/classes/external/exporter.php b/lib/classes/external/exporter.php
index 38c195a5964..2eee814846d 100644
--- a/lib/classes/external/exporter.php
+++ b/lib/classes/external/exporter.php
@@ -261,16 +261,32 @@ abstract class exporter {
     final public static function read_properties_definition() {
         $properties = static::properties_definition();
         $customprops = static::define_other_properties();
-        foreach ($customprops as $property => $definition) {
+        $customprops = static::format_properties($customprops);
+        $properties += $customprops;
+        return $properties;
+    }
+
+    /**
+     * Recursively formats a given property definition with the default fields required.
+     *
+     * @param array $properties List of properties to format
+     * @return array Formatted array
+     */
+    final public static function format_properties($properties) {
+        foreach ($properties as $property => $definition) {
             // Ensures that null is set to its default.
             if (!isset($definition['null'])) {
-                $customprops[$property]['null'] = NULL_NOT_ALLOWED;
+                $properties[$property]['null'] = NULL_NOT_ALLOWED;
             }
             if (!isset($definition['description'])) {
-                $customprops[$property]['description'] = $property;
+                $properties[$property]['description'] = $property;
+            }
+
+            // If an array is provided, it may be a nested array that is unformatted so rinse and repeat.
+            if (is_array($definition['type'])) {
+                $properties[$property]['type'] = static::format_properties($definition['type']);
             }
         }
-        $properties += $customprops;
         return $properties;
     }
 
diff --git a/lib/tests/exporter_test.php b/lib/tests/exporter_test.php
index f456628946a..57929ca6d8a 100644
--- a/lib/tests/exporter_test.php
+++ b/lib/tests/exporter_test.php
@@ -179,6 +179,8 @@ class core_exporter_testcase extends advanced_testcase {
         $this->assertEquals('otherstring description', $properties['otherstring']['description']);
         // Other properties default description.
         $this->assertEquals('otherstrings', $properties['otherstrings']['description']);
+        // Assert nested elements are formatted correctly.
+        $this->assertEquals('id', $properties['nestedarray']['type']['id']['description']);
     }
 }
 
@@ -228,6 +230,13 @@ class core_testable_exporter extends \core\external\exporter {
             'otherstrings' => array(
                 'type' => PARAM_TEXT,
                 'multiple' => true
+            ),
+            'nestedarray' => array(
+                'multiple' => true,
+                'optional' => true,
+                'type' => [
+                    'id' => ['type' => PARAM_INT]
+                ]
             )
         );
     }