diff -u b/core/modules/migrate/src/MigrateExecutable.php b/core/modules/migrate/src/MigrateExecutable.php
--- b/core/modules/migrate/src/MigrateExecutable.php
+++ b/core/modules/migrate/src/MigrateExecutable.php
@@ -398,14 +398,14 @@
             $value = NULL;
             break;
           }
+          $multiple = $multiple || $plugin->multiple();
         }
-        $multiple = $plugin->multiple();
       }
       // No plugins or no value means do not set.
             $value = NULL;
             break;
           }
-          $multiple = $multiple || $plugin->multiple();
+          $multiple = $plugin->multiple();
         }
       }
       // No plugins or no value means do not set.