diff --git a/core/lib/Drupal/Core/Database/Schema.php b/core/lib/Drupal/Core/Database/Schema.php
index 6b3f61d19f..6507658a10 100644
--- a/core/lib/Drupal/Core/Database/Schema.php
+++ b/core/lib/Drupal/Core/Database/Schema.php
@@ -729,7 +729,10 @@ protected function escapeDefaultValue($value) {
    *   do not define 'not null' as TRUE.
    */
   protected function ensureNotNullPrimaryKey(array $primary_key, array $fields) {
-    foreach (array_intersect($primary_key, array_keys($fields)) as $field_name) {
+    $key_names = array_map(function ($key_spec) {
+      return is_array($key_spec) ? $key_spec[0] : $key_spec;
+    }, $primary_key);
+    foreach (array_intersect($key_names, array_keys($fields)) as $field_name) {
       if (!isset($fields[$field_name]['not null']) || $fields[$field_name]['not null'] !== TRUE) {
         throw new SchemaException("The '$field_name' field specification does not define 'not null' as TRUE.");
       }