diff --git a/core/modules/migrate/src/Plugin/migrate/source/SqlBase.php b/core/modules/migrate/src/Plugin/migrate/source/SqlBase.php
index ec22c3f65e8ad49c9bfbbea07b45af01c1d2fcc1..cf13b463921b8f7a145da03625732cb54c683f5d 100644
--- a/core/modules/migrate/src/Plugin/migrate/source/SqlBase.php
+++ b/core/modules/migrate/src/Plugin/migrate/source/SqlBase.php
@@ -452,7 +452,7 @@ protected function mapJoinable() {
     }
 
     foreach (['username', 'password', 'host', 'port', 'namespace', 'driver'] as $key) {
-      if (isset($source_database_options[$key])) {
+      if (isset($source_database_options[$key]) && isset($id_map_database_options[$key])) {
         if ($id_map_database_options[$key] != $source_database_options[$key]) {
           return FALSE;
         }