diff --git a/core/modules/migrate/src/Row.php b/core/modules/migrate/src/Row.php
index 3524ca0..95e7f28 100644
--- a/core/modules/migrate/src/Row.php
+++ b/core/modules/migrate/src/Row.php
@@ -110,10 +110,7 @@ public function __construct(array $values = [], array $source_ids = [], $is_stub
    *   in the same order as defined in $this->sourceIds.
    */
   public function getSourceIdValues() {
-    // First, return the array of keys properly ordered with
-    // array_flip(array_keys()). Then, fill in values by merging with
-    // array_intersect_key().
-    return array_merge(array_flip(array_keys($this->sourceIds)), array_intersect_key($this->source, $this->sourceIds));
+    return array_merge($this->sourceIds, array_intersect_key($this->source, $this->sourceIds));
   }
 
   /**