core/modules/rest/tests/src/Functional/CookieResourceTestTrait.php       | 1 -
 .../src/Functional/EntityResource/Comment/CommentResourceTestBase.php    | 1 -
 .../rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php  | 1 -
 3 files changed, 3 deletions(-)

diff --git a/core/modules/rest/tests/src/Functional/CookieResourceTestTrait.php b/core/modules/rest/tests/src/Functional/CookieResourceTestTrait.php
index 41fde93..bf3f318 100644
--- a/core/modules/rest/tests/src/Functional/CookieResourceTestTrait.php
+++ b/core/modules/rest/tests/src/Functional/CookieResourceTestTrait.php
@@ -65,7 +65,6 @@ protected function initAuthentication() {
 
     $request_options[RequestOptions::BODY] = $this->serializer->encode($request_body, 'json');
     $request_options[RequestOptions::HEADERS] = [
-      'Accept' => 'application/json',
       'Content-Type' => 'application/json',
     ];
     $response = $this->request('POST', $user_login_url, $request_options);
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentResourceTestBase.php
index ecae9f8..4d3a92c 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentResourceTestBase.php
@@ -271,7 +271,6 @@ public function testPostDxWithoutCriticalBaseFields() {
 
     $url = $this->getPostUrl()->setOption('query', ['_format' => static::$format]);
     $request_options = [];
-    $request_options[RequestOptions::HEADERS]['Accept'] = static::$mimeType;
     $request_options[RequestOptions::HEADERS]['Content-Type'] = static::$mimeType;
     $request_options = array_merge_recursive($request_options, $this->getAuthenticationRequestOptions('POST'));
 
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
index 603fb35..10fef3f 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
@@ -441,7 +441,6 @@ public function testGet() {
     $this->assertNotSame([static::$mimeType], $response->getHeader('Content-Type'));
 
 
-    $request_options[RequestOptions::HEADERS]['Accept'] = static::$mimeType;
 
 
     // DX: 406 when requesting unsupported format but specifying Accept header.