diff --git a/test/Tests/Feature/Actions/GetMappingsTest.php b/test/Tests/Feature/Actions/GetMappingsTest.php
index 9dcc7e7..eadc3c7 100644
--- a/test/Tests/Feature/Actions/GetMappingsTest.php
+++ b/test/Tests/Feature/Actions/GetMappingsTest.php
@@ -22,6 +22,7 @@ public function testActionCanSetTimestampsAsDate()
         $mappings = $action(setTimestampsToDate: true);
 
         $this->assertArrayHasKey('date', $mappings);
+        $this->assertArrayHasKey('immutable_date', $mappings);
         $this->assertArrayHasKey('datetime', $mappings);
         $this->assertArrayHasKey('immutable_datetime', $mappings);
         $this->assertArrayHasKey('immutable_custom_datetime', $mappings);