diff --git a/CHANGELOG.md b/CHANGELOG.md
index 93149158..0e0ab6dc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Cast `$_SERVER['SERVER_PORT']` to integer to prevent adding 80 or 443 port to redirect URL. #403
 - Check subject when verifying JWT #406
 
+### Fixed
+- Changed parameter #2 of http_build_query to empty string on requestTokenExchange to support PHP8.x
+
 ## [1.0.0] - 2023-12-13
 
 ### Added
diff --git a/src/OpenIDConnectClient.php b/src/OpenIDConnectClient.php
index abb37d8e..fcb66996 100644
--- a/src/OpenIDConnectClient.php
+++ b/src/OpenIDConnectClient.php
@@ -972,7 +972,7 @@ public function requestTokenExchange(string $subjectToken, string $subjectTokenT
         }
 
         // Convert token params to string format
-        $post_params = http_build_query($post_data, null, '&', $this->encType);
+        $post_params = http_build_query($post_data, '', '&', $this->encType);
 
         return json_decode($this->fetchURL($token_endpoint, $post_params, $headers), false);
     }