diff --git a/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php b/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
index 37efb97..6e6e30e 100644
--- a/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
+++ b/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
@@ -278,6 +278,11 @@ class Schema extends DatabaseSchema {
         $keys[] = 'INDEX `' . $index . '` (' . $this->createKeysSqlHelper($fields) . ')';
       }
     }
+    if (!empty($spec['foreign keys'])) {
+      foreach ($spec['foreign keys'] as $key => $definition) {
+        $keys[] = 'FOREIGN KEY (`' . implode('`, `', array_keys($definition['columns'])) . '`) REFERENCES ' . $definition['table'] . '(`' . implode('`, `', $definition['columns']) . '`)';
+      }
+    }
 
     return $keys;
   }