diff --git a/src/Payone/Payone/Api/Request.php b/src/Payone/Payone/Api/Request.php
index 7c5fe7a..1113abc 100644
--- a/src/Payone/Payone/Api/Request.php
+++ b/src/Payone/Payone/Api/Request.php
@@ -150,7 +150,7 @@ public function get_key() {
 	 * @return Request
 	 */
 	public function set_key( $key ) {
-		$this->set( 'key', hash( 'sha384', $key ) );
+		$this->set( 'key', hash( 'sha384', html_entity_decode( $key ) ) );
 
 		return $this;
 	}