diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,13 @@
 Changes
 =======
 
+Version 0.2.4
+-------------
+
+* Add `customMain`
+* Fix a bug where only one of multiple output files with the same base name but
+  different extensions would be copied on installation
+
 Version 0.2.3.4
 ---------------
 
diff --git a/haskell-packages.cabal b/haskell-packages.cabal
--- a/haskell-packages.cabal
+++ b/haskell-packages.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                haskell-packages
-version:             0.2.3.4
+version:             0.2.4
 synopsis:            Haskell suite library for package management and integration with Cabal
 description:         See <http://documentup.com/haskell-suite/haskell-packages>
 license:             MIT
diff --git a/src/Distribution/HaskellSuite/Cabal.hs b/src/Distribution/HaskellSuite/Cabal.hs
--- a/src/Distribution/HaskellSuite/Cabal.hs
+++ b/src/Distribution/HaskellSuite/Cabal.hs
@@ -2,7 +2,7 @@
 {-# LANGUAGE DeriveDataTypeable, ScopedTypeVariables #-}
 
 module Distribution.HaskellSuite.Cabal
-  ( main )
+  ( main, customMain )
   where
 
 import Data.Typeable
@@ -39,7 +39,13 @@
 main
   :: forall c . Compiler.Is c
   => c -> IO ()
-main t =
+main = customMain empty
+
+customMain
+  :: forall c . Compiler.Is c
+  => Parser (IO ())
+  -> c -> IO ()
+customMain additionalActions t =
   join $ customExecParser (prefs noBacktrack) $ info (helper <*> optParser) idm
   where
 
@@ -51,6 +57,7 @@
       , supportedLanguages
       , supportedExtensions
       , hsubparser $ pkgCommand <> compilerCommand
+      , additionalActions
       ]
 
   versionStr = showVersion $ Compiler.version t
diff --git a/src/Distribution/HaskellSuite/Cabal.hs-boot b/src/Distribution/HaskellSuite/Cabal.hs-boot
--- a/src/Distribution/HaskellSuite/Cabal.hs-boot
+++ b/src/Distribution/HaskellSuite/Cabal.hs-boot
@@ -1,7 +1,12 @@
 module Distribution.HaskellSuite.Cabal where
 
 import {-# SOURCE #-} qualified Distribution.HaskellSuite.Compiler as Compiler
+import Options.Applicative
 
 main
   :: Compiler.Is c
   => c -> IO ()
+customMain
+  :: Compiler.Is c
+  => Parser (IO ())
+  -> c -> IO ()
diff --git a/src/Distribution/HaskellSuite/Compiler.hs b/src/Distribution/HaskellSuite/Compiler.hs
--- a/src/Distribution/HaskellSuite/Compiler.hs
+++ b/src/Distribution/HaskellSuite/Compiler.hs
@@ -18,6 +18,7 @@
   -- It parses command line options (that are typically passed by Cabal) and
   -- invokes the appropriate compiler's methods.
   , main
+  , customMain
   )
   where
 
@@ -93,8 +94,10 @@
       -> [ModuleName]
       -> IO ()
   installLib t buildDir targetDir _dynlibTargetDir _pkg mods =
-    findModuleFiles [buildDir] (fileExtensions t) mods
-      >>= installOrdinaryFiles normal targetDir
+    -- see https://github.com/haskell-suite/haskell-packages/pull/17
+    forM_ (fileExtensions t) $ \ext -> do
+      findModuleFiles [buildDir] [ext] mods
+        >>= installOrdinaryFiles normal targetDir
 
   -- | Register the package in the database. If a package with the same id
   -- is already installed, it should be replaced by the new one.