diff --git a/CHANGELOG.md b/CHANGELOG.md
index 93149158..7834a82b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 [unreleased]
+
+### Fixed
+- Return types are too strict. #412
 - Updated CI to also test on PHP 8.3 #407
 - Updated readme PHP requirement to PHP 7.0+ #407
 - Added dependabot for GitHub Actions #407
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index df8ef259..ce4a62c6 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -9,20 +9,10 @@
         stopOnFailure="false"
         processIsolation="false"
         backupGlobals="false"
-        syntaxCheck="true"
 >
     <testsuites>
         <testsuite name="Tests">
             <directory>./tests</directory>
         </testsuite>
     </testsuites>
-    <filter>
-        <whitelist addUncoveredFilesFromWhitelist="true">
-            <directory suffix=".php">./src</directory>
-            <exclude>
-                <directory>./vendor</directory>
-                <directory>./tests</directory>
-            </exclude>
-        </whitelist>
-    </filter>
 </phpunit>
diff --git a/src/OpenIDConnectClient.php b/src/OpenIDConnectClient.php
index abb37d8e..37b84886 100644
--- a/src/OpenIDConnectClient.php
+++ b/src/OpenIDConnectClient.php
@@ -1224,9 +1224,9 @@ protected function urlEncode(string $str): string
     /**
      * @param string $jwt encoded JWT
      * @param int $section the section we would like to decode
-     * @return object
+     * @return ?object
      */
-    protected function decodeJWT(string $jwt, int $section = 0): stdClass {
+    protected function decodeJWT(string $jwt, int $section = 0): ?stdClass {
 
         $parts = explode('.', $jwt);
         return json_decode(base64url_decode($parts[$section]), false);
@@ -1728,7 +1728,7 @@ public function getAccessToken(): string
         return $this->accessToken;
     }
 
-    public function getRefreshToken(): string
+    public function getRefreshToken(): ?string
     {
         return $this->refreshToken;
     }