diff --git a/classes/class-pmpromc-mailchimp-api.php b/classes/class-pmpromc-mailchimp-api.php
index ea47224..7204521 100644
--- a/classes/class-pmpromc-mailchimp-api.php
+++ b/classes/class-pmpromc-mailchimp-api.php
@@ -190,7 +190,7 @@ public function update_audience_members( $audience = '', $updates = [] ) {
 			'user-agent' => self::$user_agent,
 			'headers' => $this->url_args['headers'],
 			'timeout' => $this->url_args['timeout'],
-			'body' => json_encode($data),
+			'body' => wp_json_encode($data),
 		);
 
 		$resp = wp_remote_post($url, $args);
@@ -441,7 +441,7 @@ private function decode_response($response)
 	 */
 	private function encode($data)
 	{
-		if (false !== ($json = json_encode($data))) {
+		if (false !== ($json = wp_json_encode($data))) {
 			return $json;
 		}