diff --git a/core/modules/system/src/Tests/Entity/EntitySchemaTest.php b/core/modules/system/src/Tests/Entity/EntitySchemaTest.php
index 739ee1c..47b10ba 100644
--- a/core/modules/system/src/Tests/Entity/EntitySchemaTest.php
+++ b/core/modules/system/src/Tests/Entity/EntitySchemaTest.php
@@ -163,7 +163,7 @@ public function testCleanUpStorageDefinition() {
     $entity_type_id_count = 0;
 
     foreach (array_keys($schema) as $storage_definition_name) {
-      $entity_type_id = substr($storage_definition_name, 0, strpos($storage_definition_name, '.'));
+      list($entity_type_id, ,) = explode('.', $storage_definition_name);
       if (in_array($entity_type_id, $entity_type_ids)) {
         $entity_type_id_count++;
       }
@@ -184,7 +184,7 @@ public function testCleanUpStorageDefinition() {
     $entity_type_id_count = 0;
 
     foreach (array_keys($schema) as $storage_definition_name) {
-      $entity_type_id = substr($storage_definition_name, 0, strpos($storage_definition_name, '.'));
+      list($entity_type_id, ,) = explode('.', $storage_definition_name);
       if (in_array($entity_type_id, $entity_type_ids)) {
         $entity_type_id_count++;
       }