diff --git a/README.md b/README.md
index 7873301..5f1528f 100644
--- a/README.md
+++ b/README.md
@@ -29,8 +29,7 @@ $xmlDocument = new DOMDocument();
 $xmlDocument->load($xmlPath);
 
 $xmlTool = new SunatXmlSecAdapter();
-$xmlTool->setPrivateKey(file_get_contents($certPath));
-$xmlTool->setPublicKey(file_get_contents($certPath));
+$xmlTool->setCertificateFromFile($certPath);
 
 $xmlTool->sign($xmlDocument);