diff --git a/src/MaxCDN/OAuth/OAuthSignatureMethod.php b/src/MaxCDN/OAuth/OAuthSignatureMethod.php
index da905ff..d6bea7b 100644
--- a/src/MaxCDN/OAuth/OAuthSignatureMethod.php
+++ b/src/MaxCDN/OAuth/OAuthSignatureMethod.php
@@ -47,7 +47,7 @@ public function check_signature($request, $consumer, $token, $signature) {
         // Avoid a timing leak with a (hopefully) time insensitive compare
         $result = 0;
         for ($i = 0; $i < strlen($signature); $i++) {
-            $result |= ord($built{$i}) ^ ord($signature{$i});
+            $result |= ord($built[$i]) ^ ord($signature[$i]);
         }
 
         return $result == 0;