diff --git a/Core/tests/Unit/ClientTraitTest.php b/Core/tests/Unit/ClientTraitTest.php
index 81359ea20b0a..5d9a28ef2a55 100644
--- a/Core/tests/Unit/ClientTraitTest.php
+++ b/Core/tests/Unit/ClientTraitTest.php
@@ -168,7 +168,11 @@ public function testConfigureAuthenticationWithKeyFilePath()
 
     public function testIgnoreKeyFileWhenUsingCredentialsFetcher()
     {
-        $credentials = new ServiceAccountCredentials([], Fixtures::SERVICE_ACCOUNT_FIXTURE());
+        $keyFilePath = Fixtures::SERVICE_ACCOUNT_FIXTURE();
+        $key = json_decode(file_get_contents($keyFilePath), true);
+        $key['private_key'] = 'xxx';
+
+        $credentials = new ServiceAccountCredentials([], $key);
 
         $conf = $this->impl->call('configureAuthentication', [[
             'credentialsFetcher' => $credentials,
@@ -179,7 +183,11 @@ public function testIgnoreKeyFileWhenUsingCredentialsFetcher()
 
     public function testGetProjectIdFromCredentialsFetcher()
     {
-        $credentials = new ServiceAccountCredentials([], Fixtures::SERVICE_ACCOUNT_FIXTURE());
+        $keyFilePath = Fixtures::SERVICE_ACCOUNT_FIXTURE();
+        $key = json_decode(file_get_contents($keyFilePath), true);
+        $key['private_key'] = 'xxx';
+
+        $credentials = new ServiceAccountCredentials([], $key);
 
         $this->impl->call('configureAuthentication', [[
             'credentialsFetcher' => $credentials,
diff --git a/Core/tests/Unit/fixtures/service-account-fixture.json b/Core/tests/Unit/fixtures/service-account-fixture.json
index fa3a868fc79d..8d124ca8ac6a 100644
--- a/Core/tests/Unit/fixtures/service-account-fixture.json
+++ b/Core/tests/Unit/fixtures/service-account-fixture.json
@@ -2,7 +2,6 @@
   "type": "service_account",
   "project_id": "example-project-12345",
   "private_key_id": "1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b",
-  "private_key": "-----BEGIN PRIVATE KEY-----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\nBbFaAE9VZFi2OcxtIysoxek=\n-----END PRIVATE KEY-----\n",
   "client_email": "test-service-account@example-project-12345.iam.gserviceaccount.com",
   "client_id": "123456789012345678901",
   "auth_uri": "https://accounts.google.com/o/oauth2/auth",