diff --git a/happstack-server.cabal b/happstack-server.cabal
--- a/happstack-server.cabal
+++ b/happstack-server.cabal
@@ -1,5 +1,5 @@
 Name:                happstack-server
-Version:             7.9.2.2
+Version:             7.9.3
 Synopsis:            Web related tools and services.
 Description:         Happstack Server provides an HTTP server and a rich set of functions for routing requests, handling query parameters, generating responses, working with cookies, serving files, and more. For in-depth documentation see the Happstack Crash Course <http://happstack.com/docs/crashcourse/index.html>
 License:             BSD3
diff --git a/src/Happstack/Server/FileServe/BuildingBlocks.hs b/src/Happstack/Server/FileServe/BuildingBlocks.hs
--- a/src/Happstack/Server/FileServe/BuildingBlocks.hs
+++ b/src/Happstack/Server/FileServe/BuildingBlocks.hs
@@ -59,6 +59,7 @@
 import Control.Monad.Trans          (MonadIO(liftIO))
 import qualified Data.ByteString.Lazy.Char8 as L
 import qualified Data.ByteString.Char8 as S
+import Data.Char                    (toLower)
 import Data.Data                    (Data)
 import Data.List                    (sort)
 import Data.Maybe                   (fromMaybe)
@@ -96,7 +97,7 @@
 guessContentType mimeMap filepath =
     case getExt filepath of
       "" -> Nothing
-      ext -> Map.lookup ext mimeMap
+      ext -> Map.lookup (map toLower ext) mimeMap -- FIXME? @foldCase@ would be more proper than @map toLower@ but would add a dependency. But are those edge cases ever going to be relevant here?
 
 -- | try to guess the content-type of a file based on its extension
 --
@@ -121,7 +122,7 @@
 
 -- | a list of common index files. Specifically: @index.html@, @index.xml@, @index.gif@
 --
--- Typically used as an argument to 'serveDiretory'.
+-- Typically used as an argumebnt to 'serveDiretory'.
 defaultIxFiles :: [FilePath]
 defaultIxFiles= ["index.html","index.xml","index.gif"]
 
@@ -130,6 +131,8 @@
 fileNotFound fp = return $ result 404 $ "File not found " ++ fp
 
 -- | Similar to 'takeExtension' but does not include the extension separator char
+--
+-- NOTE: this does not perform case folding. So @example.jpg@ will return @.jpg@ and @example.JPG@ will return @.JPG@.
 getExt :: FilePath -> String
 getExt fp = drop 1 $ takeExtension fp