diff --git a/cern_integration.module b/cern_integration.module
index 30bba612719421643d18f4930c39a66025e60521..941456cd6b3a228f3c57e5d9496b9593aea00d25 100644
--- a/cern_integration.module
+++ b/cern_integration.module
@@ -76,7 +76,7 @@ function cern_integration_form_user_register_form_alter(&$form, &$form_state, $f
 * As this module injects a checkbox on user_form, cern_integration module must be unstacked.
 */
 function cern_integration_module_implements_alter(&$implementations, $hook) {
-  if ($hook == 'form_alter') {
+  if ($hook == 'form_alter' && isset($implementations['cern_integration'])) {
     // Move my_module_form_alter() to the end of the list.
     // \Drupal::moduleHandler()->getImplementations()
     // iterates through $implementations with a foreach loop which PHP iterates