diff --git a/src/wai-make-assets.hs b/src/wai-make-assets.hs
--- a/src/wai-make-assets.hs
+++ b/src/wai-make-assets.hs
@@ -1,5 +1,7 @@
 {-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE ViewPatterns #-}
 
+import           Data.Maybe
 import           Network.Wai.Handler.Warp
 import           System.IO
 import           WithCli
@@ -8,17 +10,18 @@
 
 data Args
   = Args {
-    port :: Int
+    port :: Maybe Int
   }
   deriving (Generic)
 
 instance HasArguments Args
 
 main :: IO ()
-main = withCliModified [AddShortOption "port" 'p'] $ \ (Args port) -> do
-  let settings =
-        setPort port $
-        setBeforeMainLoop (hPutStrLn stderr
-          ("listening to " ++ show port ++ "...")) $
-        defaultSettings
-  runSettings settings =<< serveAssets
+main = withCliModified [AddShortOption "port" 'p'] $
+  \ (Args (fromMaybe 8000 -> port)) -> do
+    let settings =
+          setPort port $
+          setBeforeMainLoop (hPutStrLn stderr
+            ("listening to " ++ show port ++ "...")) $
+          defaultSettings
+    runSettings settings =<< serveAssets
diff --git a/wai-make-assets.cabal b/wai-make-assets.cabal
--- a/wai-make-assets.cabal
+++ b/wai-make-assets.cabal
@@ -3,7 +3,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           wai-make-assets
-version:        0.1
+version:        0.1.1
 synopsis:       Compiling and serving assets
 description:    Small wai library and command line tool for compiling and serving assets (e.g. through ghcjs, elm, sass)
 category:       Development