diff --git a/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php b/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
index 8f5b710..c2d2ed1 100644
--- a/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
+++ b/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
@@ -276,10 +276,12 @@ protected function createKeysSql($spec) {
     $keys = array();
 
     if (!empty($spec['primary key'])) {
-      $keys[] = 'PRIMARY KEY (' . $this->createKeySql($spec['primary key']) . ')';
+      $primary_key = $this->getNormalizedIndexes($spec, 'primary key');
+      $keys[] = 'PRIMARY KEY (' . $this->createKeySql($primary_key) . ')';
     }
     if (!empty($spec['unique keys'])) {
-      foreach ($spec['unique keys'] as $key => $fields) {
+      $unique_keys = $this->getNormalizedIndexes($spec, 'unique keys');
+      foreach ($unique_keys as $key => $fields) {
         $keys[] = 'UNIQUE KEY `' . $key . '` (' . $this->createKeySql($fields) . ')';
       }
     }
@@ -301,12 +303,15 @@ protected function createKeysSql($spec) {
    *
    * @param $spec
    *   The table specification.
+   * @param string $index_type
+   *   The index type. Defaults to 'indexes', but can also be 'unique keys' or
+   *   'primary key'.
    *
    * @return array
    *   List of shortened indexes.
    */
-  protected function getNormalizedIndexes($spec) {
-    $indexes = $spec['indexes'];
+  protected function getNormalizedIndexes($spec, $index_type = 'indexes') {
+    $indexes = $index_type === 'primary key' ? ['primary key' => $spec[$index_type]] : $spec[$index_type];
     foreach ($indexes as $index_name => $index_fields) {
       foreach ($index_fields as $index_key => $index_field) {
         // Get the name of the field from the index specification.
@@ -325,7 +330,7 @@ protected function getNormalizedIndexes($spec) {
         }
       }
     }
-    return $indexes;
+    return $index_type === 'primary key' ? $indexes['primary key'] : $indexes;
   }
 
   /**