diff --git a/Yesod/Default/Config.hs b/Yesod/Default/Config.hs
--- a/Yesod/Default/Config.hs
+++ b/Yesod/Default/Config.hs
@@ -70,7 +70,7 @@
     getPort front (arg:rest) = getPort (front . (arg:)) rest
 
     capitalize [] = []
-    capitalize (x:xs) = toUpper x : map toLower xs
+    capitalize (x:xs) = toUpper x : xs
 
 -- | Load the app config from command line parameters, using the given
 -- @ConfigSettings.
diff --git a/yesod.cabal b/yesod.cabal
--- a/yesod.cabal
+++ b/yesod.cabal
@@ -1,5 +1,5 @@
 name:            yesod
-version:         1.2.2.1
+version:         1.2.3
 license:         MIT
 license-file:    LICENSE
 author:          Michael Snoyman <michael@snoyman.com>