diff --git a/lib/MetaCPAN/Server/Controller/OAuth2.pm b/lib/MetaCPAN/Server/Controller/OAuth2.pm
index f044c443a..f9e592a82 100644
--- a/lib/MetaCPAN/Server/Controller/OAuth2.pm
+++ b/lib/MetaCPAN/Server/Controller/OAuth2.pm
@@ -109,7 +109,7 @@ sub bad_request {
 
 sub _build_code {
     my $digest = Digest::SHA::sha1_base64( rand() . $$ . {} . time );
-    $digest =~ tr/[+\/]/-_/;
+    $digest =~ tr{+/}{-_};
     return $digest;
 }