diff --git a/user/classes/fields.php b/user/classes/fields.php
index 20c92d20fc6..c4154d83308 100644
--- a/user/classes/fields.php
+++ b/user/classes/fields.php
@@ -377,9 +377,13 @@ class fields {
                 $allowed = false;
                 if ($allowcustom) {
                     require_once($CFG->dirroot . '/user/profile/lib.php');
+
+                    // Ensure the field exists (it may have been deleted since user identity was configured).
                     $field = profile_get_custom_field_data_by_shortname($matches[1], false);
-                    $fieldinstance = profile_get_user_field($field->datatype, $field->id, 0, $field);
-                    $allowed = $fieldinstance->is_visible($context);
+                    if ($field !== null) {
+                        $fieldinstance = profile_get_user_field($field->datatype, $field->id, 0, $field);
+                        $allowed = $fieldinstance->is_visible($context);
+                    }
                 }
                 if (!$allowed) {
                     unset($extra[$key]);
diff --git a/user/tests/fields_test.php b/user/tests/fields_test.php
index d046ee1bf15..1d7977be335 100644
--- a/user/tests/fields_test.php
+++ b/user/tests/fields_test.php
@@ -22,6 +22,7 @@ namespace core_user;
  * @package core
  * @copyright 2014 The Open University
  * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ * @covers \core_user\fields
  */
 class fields_test extends \advanced_testcase {
 
@@ -153,6 +154,27 @@ class fields_test extends \advanced_testcase {
                 fields::get_identity_fields($usercontext, false));
     }
 
+    /**
+     * Test getting identity fields, when one of them refers to a non-existing custom profile field
+     */
+    public function test_get_identity_fields_invalid(): void {
+        $this->resetAfterTest();
+
+        $this->getDataGenerator()->create_custom_profile_field([
+            'datatype' => 'text',
+            'shortname' => 'real',
+            'name' => 'I\'m real',
+        ]);
+
+        // The "fake" profile field does not exist.
+        set_config('showuseridentity', 'email,profile_field_real,profile_field_fake');
+
+        $this->assertEquals([
+            'email',
+            'profile_field_real',
+        ], fields::get_identity_fields(null));
+    }
+
     /**
      * Tests the get_required_fields function.
      *