diff --git a/core/modules/rest/src/Tests/ReadTest.php b/core/modules/rest/src/Tests/ReadTest.php
index c59d64f..de6883a 100644
--- a/core/modules/rest/src/Tests/ReadTest.php
+++ b/core/modules/rest/src/Tests/ReadTest.php
@@ -95,7 +95,7 @@ public function testRead() {
     // application/hal+json, so it returns a 406.
     $this->assertResponse('406', 'HTTP response code is 406 when the resource does not define formats, because it falls back to the canonical, non-REST route.');
     $this->assertEqual($response, Json::encode([
-      'message' => 'Not acceptable',
+      'message' => 'Not acceptable format: hal_json',
     ]));
   }