diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,17 +2,34 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
-## 0.2.0 - 2015-06-01
+## [0.3.0] - 2015-07-10
+### Added
+- Support for a `ByteString` result (thanks to [Andy
+  Morris](https://github.com/jakubfijalkowski/hsass/pull/3) ).
+
 ### Changed
-- Return type of 'compileString' and 'compileFile' is now polymorphic - may
-  return both 'String' and 'SassExtendedResult' on success.
+- `SassExtendedResult` is now parametrised by a base result type (e.g.
+  `String`).
+- The package depends on `transformers` instead of `mtl`.
+
+### Fixed
+- Fix GHC 7.10.1 warnings related to AMP proposal.
+- Support for stack's lts-2.17 resolver.
+
+## [0.2.0] - 2015-06-01
+### Changed
+- Return type of `compileString` and `compileFile` is now polymorphic - may
+  return both `String` and `SassExtendedResult` on success.
 - Fixes in documentation (articles, mostly).
 
 ### Added
-- 'SassExtendedResult' with a compiled string, a list of files included during
+- `SassExtendedResult` with a compiled string, a list of files included during
   compilation and a source map.
 
 ## 0.1.0 - 2015-04-11
 ### Added
 - Support for functions, importers, headers and sass values.
 - Compilation of files and strings.
+
+[0.2.0]: https://github.com/jakubfijalkowski/hsass/compare/v0.1.0...v0.2.0
+[0.3.0]: https://github.com/jakubfijalkowski/hsass/compare/v0.2.0...v0.3.0
diff --git a/Text/Sass/Compilation.hs b/Text/Sass/Compilation.hs
--- a/Text/Sass/Compilation.hs
+++ b/Text/Sass/Compilation.hs
@@ -1,5 +1,6 @@
 -- | Compilation of sass source or sass files.
 {-# LANGUAGE BangPatterns         #-}
+{-# LANGUAGE CPP                  #-}
 {-# LANGUAGE FlexibleInstances    #-}
 {-# LANGUAGE TypeSynonymInstances #-}
 module Text.Sass.Compilation
@@ -11,6 +12,7 @@
   , SassExtendedResult
   , StringResult
   , ExtendedResult
+  , ExtendedResultBS
   , resultString
   , resultIncludes
   , resultSourcemap
@@ -27,7 +29,10 @@
   ) where
 
 import qualified Bindings.Libsass    as Lib
+import           Data.ByteString     (ByteString, packCString)
+#if !MIN_VERSION_base(4,8,0)
 import           Control.Applicative ((<$>))
+#endif
 import           Control.Monad       (forM, (>=>))
 import           Foreign
 import           Foreign.C
@@ -40,31 +45,38 @@
     errorContext :: ForeignPtr Lib.SassContext
 }
 
--- | Represents extended result - compiled string with a list of includes and
--- a source map.
+-- | Represents extended result - compiled string (or other string-like type,
+-- eg. 'ByteString') with a list of includes and a source map.
 --
--- Subject to name change in future versions.
-data SassExtendedResult = SassExtendedResult {
-    resultString  :: String, -- ^ Compiled string.
+-- Subject to name change in future.
+data SassExtendedResult a = SassExtendedResult {
+    resultString  :: a, -- ^ Compiled string.
     resultContext :: ForeignPtr Lib.SassContext
 }
 
 -- | Result of compilation - 'Either' 'SassError' or a compiled string.
 --
--- Subject to name change in future versions.
+-- Subject to name change in future.
 type StringResult = IO (Either SassError String)
 
 -- | Result of compilation - 'Either' 'SassError' or extended results - a
 -- compiled string with a list of included files and a source map.
 --
--- Subject to name change in future versions.
-type ExtendedResult = IO (Either SassError SassExtendedResult)
+-- Subject to name change in future.
+type ExtendedResult = IO (Either SassError (SassExtendedResult String))
+--
+-- | Result of compilation - 'Either' 'SassError' or extended results - a
+-- compiled 'ByteString' with a list of included files and a source map.
+--
+-- Subject to name change in future.
+type ExtendedResultBS = IO (Either SassError (SassExtendedResult ByteString))
 
 -- | Typeclass that allows multiple results from compilation functions.
 --
--- Currently, only two types are supported - 'String' and 'SassExtendedResult'.
--- The first provides only a compiled string, the latter one gives access to a
--- list of included files and a source map (if available).
+-- Currently, only three types are supported - 'String', 'ByteString' and
+-- @'SassExtendedResult' a@ (where a is something that is an instance of
+-- 'SassResult').  The first provides only a compiled string, the latter one
+-- gives access to a list of included files and a source map (if available).
 class SassResult a where
     toSassResult :: ForeignPtr Lib.SassContext -> IO a
 
@@ -75,7 +87,7 @@
 instance Eq SassError where
     (SassError s1 _) == (SassError s2 _) = s1 == s2
 
-instance Show SassExtendedResult where
+instance Show (SassExtendedResult a) where
     show _ = "SassExtendedResult"
 
 -- | Only compiled code.
@@ -85,8 +97,15 @@
         !result' <- peekCString result
         return result'
 
+-- | Only compiled code (UTF-8 encoding).
+instance SassResult ByteString where
+    toSassResult ptr = withForeignPtr ptr $ \ctx -> do
+        result <- Lib.sass_context_get_output_string ctx
+        !result' <- packCString result
+        return result'
+
 -- | Compiled code with includes and a source map.
-instance SassResult SassExtendedResult where
+instance (SassResult a) => SassResult (SassExtendedResult a) where
     toSassResult ptr = do
         str <- toSassResult ptr
         return $ SassExtendedResult str ptr
@@ -142,14 +161,14 @@
 errorColumn = loadIntFromError Lib.sass_context_get_error_column
 
 -- | Loads a list of files that have been included during compilation.
-resultIncludes :: SassExtendedResult -> IO [String]
+resultIncludes :: SassExtendedResult a -> IO [String]
 resultIncludes ex = withForeignPtr (resultContext ex) $ \ctx -> do
     lst <- Lib.sass_context_get_included_files ctx
     len <- Lib.sass_context_get_included_files_size ctx
     forM (arrayRange $ fromIntegral len) (peekElemOff lst >=> peekCString)
 
 -- | Loads a source map if it was generated by libsass.
-resultSourcemap :: SassExtendedResult -> IO (Maybe String)
+resultSourcemap :: SassExtendedResult a -> IO (Maybe String)
 resultSourcemap ex = withForeignPtr (resultContext ex) $ \ctx -> do
     cstr <- Lib.sass_context_get_source_map_string ctx
     if cstr == nullPtr
diff --git a/Text/Sass/Options/Internal.hs b/Text/Sass/Options/Internal.hs
--- a/Text/Sass/Options/Internal.hs
+++ b/Text/Sass/Options/Internal.hs
@@ -1,6 +1,7 @@
 -- | Copying 'SassOptions' into native context. This module is internal and
 -- should not be considered stable.
 {-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE CPP          #-}
 module Text.Sass.Options.Internal
   (
     copyOptionsToNative
@@ -8,7 +9,9 @@
   ) where
 
 import qualified Bindings.Libsass             as Lib
+#if !MIN_VERSION_base(4,8,0)
 import           Control.Applicative          ((<$>))
+#endif
 import           Control.Monad                ((>=>))
 import           Foreign
 import           Foreign.C
diff --git a/Text/Sass/Utils.hs b/Text/Sass/Utils.hs
--- a/Text/Sass/Utils.hs
+++ b/Text/Sass/Utils.hs
@@ -1,5 +1,6 @@
 -- | Helper functions. This module is internal and should not be used in
 -- production code.
+{-# LANGUAGE CPP #-}
 module Text.Sass.Utils
   (
     -- * Interoperation with C API
@@ -12,12 +13,23 @@
   , arrayRange
   ) where
 
-import           Control.Monad.Loops        (whileM_)
-import           Control.Monad.State.Strict
-import           Data.List                  (intercalate)
+import           Control.Monad                    (zipWithM_, (>=>))
+import           Control.Monad.IO.Class
+import           Control.Monad.Loops              (whileM_)
+import           Control.Monad.Trans.Class
+import           Control.Monad.Trans.State.Strict
+import           Data.List                        (intercalate)
 import           Foreign
 import           Foreign.C
-import           System.FilePath            (searchPathSeparator)
+import           System.FilePath                  (searchPathSeparator)
+
+-- Fix for transformers-0.3.0.0 (used by lts-2.17 in stack).
+#if !MIN_VERSION_transformers(0,4,0)
+modify' :: (Monad m) => (s -> s) -> StateT s m ()
+modify' f = do
+    s <- get
+    put $! f s
+#endif
 
 -- | 'withOptionalCString' @str action@, if @str@ is 'Nothing', @action@ is not
 -- invoked, otherwise behaves like 'withCString'.
diff --git a/Text/Sass/Values/Internal.hs b/Text/Sass/Values/Internal.hs
--- a/Text/Sass/Values/Internal.hs
+++ b/Text/Sass/Values/Internal.hs
@@ -1,5 +1,6 @@
 -- | Conversion of 'SassValue' or list of 'SassValue's into native
 -- representation. This module is internal and should not be considered stable.
+{-# LANGUAGE CPP #-}
 module Text.Sass.Values.Internal
   (
     toNativeValue
@@ -9,7 +10,9 @@
   ) where
 
 import qualified Bindings.Libsass    as Lib
+#if !MIN_VERSION_base(4,8,0)
 import           Control.Applicative ((<$>))
+#endif
 import           Control.Monad       (forM, (>=>))
 import           Foreign
 import           Foreign.C
diff --git a/hsass.cabal b/hsass.cabal
--- a/hsass.cabal
+++ b/hsass.cabal
@@ -1,5 +1,5 @@
 name:                hsass
-version:             0.2.0
+version:             0.3.0
 license:             MIT
 license-file:        LICENSE
 author:              Jakub Fijałkowski <fiolek94@gmail.com>
@@ -46,13 +46,15 @@
     , Text.Sass.Values.Internal
     , Text.Sass.Utils
   build-depends:
-    base               >= 4.7 && < 5,
-    hlibsass           >= 0.1.1,
-    data-default-class,
-    filepath           >= 1.0,
-    mtl                >= 2.2,
-    monad-loops        >= 0.3
+      base               >= 4.7 && < 5
+    , hlibsass           >= 0.1.1
+    , bytestring         >= 0.10.0
+    , data-default-class
+    , filepath           >= 1.0
+    , transformers       >= 0.3
+    , monad-loops        >= 0.3
   hs-source-dirs:      .
+  other-extensions:    CPP
   default-language:    Haskell2010
   ghc-options:         -Wall
 
@@ -63,6 +65,7 @@
   ghc-options:         -Wall
   build-depends:
       base               >= 4.7 && < 5
+    , bytestring         >= 0.10.0
     , hspec              >= 2.1.5
     , hspec-discover     >= 2.1.5
     , temporary          >= 1.1