diff --git a/enrol/meta/locallib.php b/enrol/meta/locallib.php
index 7dd4a92dd2d..74a604f18e3 100644
--- a/enrol/meta/locallib.php
+++ b/enrol/meta/locallib.php
@@ -173,8 +173,8 @@ class enrol_meta_handler {
             $ue->userid = $userid;
             $ue->enrolid = $instance->id;
             $ue->status = $parentstatus;
-            if ($instance->customint2) {
-                groups_add_member($instance->customint2, $userid, 'enrol_meta', $instance->id);
+            if ($instance->customint2 && $group = $DB->get_record('groups', ['id' => $instance->customint2])) {
+                groups_add_member($group, $userid, 'enrol_meta', $instance->id);
             }
         }
 
@@ -346,8 +346,8 @@ function enrol_meta_sync($courseid = NULL, $verbose = false) {
         $ue->timestart = ($ue->timestart == 9999999999) ? 0 : (int)$ue->timestart;
 
         $meta->enrol_user($instance, $ue->userid, null, $ue->timestart, $ue->timeend, $ue->status);
-        if ($instance->customint2) {
-            groups_add_member($instance->customint2, $ue->userid, 'enrol_meta', $instance->id);
+        if ($instance->customint2 && $group = $DB->get_record('groups', ['id' => $instance->customint2])) {
+            groups_add_member($group, $ue->userid, 'enrol_meta', $instance->id);
         }
         if ($verbose) {
             mtrace("  enrolling: $ue->userid ==> $instance->courseid");
diff --git a/enrol/meta/tests/plugin_test.php b/enrol/meta/tests/plugin_test.php
index 163cb791a3f..9c12c1ef210 100644
--- a/enrol/meta/tests/plugin_test.php
+++ b/enrol/meta/tests/plugin_test.php
@@ -16,6 +16,9 @@
 
 namespace enrol_meta;
 
+use context_course;
+use enrol_meta_plugin;
+
 /**
  * Meta enrolment sync functional test.
  *
@@ -594,6 +597,40 @@ class plugin_test extends \advanced_testcase {
 
     }
 
+    /**
+     * Test enrolling users in a course, where the customint2 (group) property of the instance points to an invalid group
+     *
+     * @covers \enrol_meta_handler::sync_with_parent_course
+     * @covers ::enrol_meta_sync
+     */
+    public function test_add_to_group_invalid(): void {
+        $this->resetAfterTest();
+
+        $this->enable_plugin();
+
+        $courseone = $this->getDataGenerator()->create_course();
+        $coursetwo = $this->getDataGenerator()->create_course();
+
+        /** @var enrol_meta_plugin $plugin */
+        $plugin = enrol_get_plugin('meta');
+        $plugin->add_instance($coursetwo, ['customint1' => $courseone->id, 'customint2' => 42]);
+
+        // Ensure the event observer works for invalid groups.
+        $userone = $this->getDataGenerator()->create_and_enrol($courseone);
+
+        // Now disable the plugin, add another enrolment.
+        $this->disable_plugin();
+        $usertwo = $this->getDataGenerator()->create_and_enrol($courseone);
+
+        // Re-enable the plugin, run sync task - should also work for invalid groups.
+        $this->enable_plugin();
+        enrol_meta_sync($coursetwo->id);
+
+        $coursetwocontext = context_course::instance($coursetwo->id);
+        $this->assertTrue(is_enrolled($coursetwocontext, $userone));
+        $this->assertTrue(is_enrolled($coursetwocontext, $usertwo));
+    }
+
     /**
      * Test user_enrolment_created event.
      */