diff --git a/core/modules/migrate/src/Plugin/migrate/source/SqlBase.php b/core/modules/migrate/src/Plugin/migrate/source/SqlBase.php
index b29e736..dcef9b3 100644
--- a/core/modules/migrate/src/Plugin/migrate/source/SqlBase.php
+++ b/core/modules/migrate/src/Plugin/migrate/source/SqlBase.php
@@ -75,7 +75,7 @@ public static function create(ContainerInterface $container, array $configuratio
    *   The query string.
    */
   public function __toString() {
-    return (string) $this->query;
+    return (string) $this->query();
   }
 
   /**