diff -u b/core/modules/migrate/src/Plugin/Migration.php b/core/modules/migrate/src/Plugin/Migration.php
--- b/core/modules/migrate/src/Plugin/Migration.php
+++ b/core/modules/migrate/src/Plugin/Migration.php
@@ -663,7 +663,7 @@
    */
   public function getMigrationDependencies() {
     $this->migration_dependencies = ($this->migration_dependencies ?: []) + ['required' => [], 'optional' => []];
-    $this->migration_dependencies['optional'] = array_unique(array_merge($this->migration_dependencies['optional'], $this->findMigrationDependencies($this->getProcess())));
+    $this->migration_dependencies['optional'] = array_unique(array_merge($this->migration_dependencies['optional'], $this->findMigrationDependencies($this->process)));
     return $this->migration_dependencies;
   }
 
@@ -675,13 +675,13 @@
    */
   protected function findMigrationDependencies($process) {
     $return = [];
-    foreach ($process as $process_pipeline) {
+    foreach ($this->getProcessNormalized($process) as $process_pipeline) {
       foreach ($process_pipeline as $plugin_configuration) {
         if ($plugin_configuration['plugin'] == 'migration') {
           $return = array_merge($return, (array) $plugin_configuration['migration']);
         }
         if ($plugin_configuration['plugin'] == 'iterator') {
-          $return = array_merge($return, $this->findMigrationDependencies($this->getProcessNormalized($plugin_configuration['process'])));
+          $return = array_merge($return, $this->findMigrationDependencies($plugin_configuration['process']));
         }
       }
     }