diff --git a/tests/Grant/AuthCodeGrantTest.php b/tests/Grant/AuthCodeGrantTest.php
index 4ea0a5d0..07b220c5 100644
--- a/tests/Grant/AuthCodeGrantTest.php
+++ b/tests/Grant/AuthCodeGrantTest.php
@@ -771,6 +771,7 @@ class AuthCodeGrantTest extends TestCase
         $grant->setScopeRepository($scopeRepositoryMock);
         $grant->setAccessTokenRepository($accessTokenRepositoryMock);
         $grant->setEncryptionKey($this->cryptStub->getKey());
+        $grant->setPrivateKey(new CryptKey('file://' . __DIR__ . '/../Stubs/private.key'));
 
         $request = new ServerRequest(
             [],
diff --git a/tests/Grant/PasswordGrantTest.php b/tests/Grant/PasswordGrantTest.php
index e8843c74..7fc99e83 100644
--- a/tests/Grant/PasswordGrantTest.php
+++ b/tests/Grant/PasswordGrantTest.php
@@ -108,6 +108,7 @@ class PasswordGrantTest extends TestCase
         $grant->setAccessTokenRepository($accessTokenRepositoryMock);
         $grant->setScopeRepository($scopeRepositoryMock);
         $grant->setDefaultScope(self::DEFAULT_SCOPE);
+        $grant->setPrivateKey(new CryptKey('file://' . __DIR__ . '/../Stubs/private.key'));
 
         $serverRequest = new ServerRequest();
         $serverRequest = $serverRequest->withParsedBody(