diff --git a/ApiAwareTrait.php b/ApiAwareTrait.php
index 6207c3a..0d262c0 100644
--- a/ApiAwareTrait.php
+++ b/ApiAwareTrait.php
@@ -3,6 +3,8 @@
 
 use Payum\Core\Exception\LogicException;
 use Payum\Core\Exception\UnsupportedApiException;
+use function get_class;
+use function is_object;
 
 trait ApiAwareTrait
 {
@@ -30,7 +32,7 @@ public function setApi($api)
         }
 
         if (!$api instanceof $this->apiClass) {
-            throw new UnsupportedApiException(sprintf('Not supported api given. It must be an instance of %s', $this->apiClass));
+            throw new UnsupportedApiException(sprintf('Not supported api given. It must be an instance of %s', is_object($this->apiClass) ? get_class($this->apiClass) : $this->apiClass));
         }
 
         $this->api = $api;