diff --git a/README.md b/README.md
index 8c839d2..726e91c 100644
--- a/README.md
+++ b/README.md
@@ -27,3 +27,8 @@ Benchmark results:
 
 But if you really really really need backtracking, then you can just
 inject attoparsec parser into a scanner: http://hackage.haskell.org/package/scanner-attoparsec
+
+# MicroHs
+
+The library should compile and work with MicroHs.
+To run the test suite: `mhs -icompat -iportable_hspec -ilib -r spec/spec.hs`
diff --git a/compat/Data/ByteString/Lazy_.hs b/compat/Data/ByteString/Lazy_.hs
new file mode 100644
index 0000000..8654fa9
--- /dev/null
+++ b/compat/Data/ByteString/Lazy_.hs
@@ -0,0 +1,22 @@
+{-# LANGUAGE PackageImports #-}
+{-# LANGUAGE CPP #-}
+
+module Data.ByteString.Lazy_
+( ByteString
+, toChunks
+, fromChunks
+) where
+
+#ifdef __MHS__
+import qualified Data.ByteString as Strict
+
+newtype ByteString = ByteString [Strict.ByteString]
+
+toChunks :: ByteString -> [Strict.ByteString]
+toChunks (ByteString chunks) = chunks
+
+fromChunks :: [Strict.ByteString] -> ByteString
+fromChunks = ByteString
+#else
+import "bytestring" Data.ByteString.Lazy
+#endif
diff --git a/compat/GHC/Base.hs b/compat/GHC/Base.hs
new file mode 100644
index 0000000..102f089
--- /dev/null
+++ b/compat/GHC/Base.hs
@@ -0,0 +1,14 @@
+{-# LANGUAGE PackageImports #-}
+{-# LANGUAGE CPP #-}
+
+module GHC.Base
+( unsafeChr
+) where
+
+#ifdef __MHS__
+import Data.Char
+unsafeChr :: Int -> Char
+unsafeChr = chr
+#else
+import "base" GHC.Base
+#endif
diff --git a/lib/Scanner.hs b/lib/Scanner.hs
index 7cfd18f..f1e0012 100644
--- a/lib/Scanner.hs
+++ b/lib/Scanner.hs
@@ -42,8 +42,8 @@ import Data.Word
 import qualified Data.Char as Char
 import Data.ByteString (ByteString)
 import qualified Data.ByteString as ByteString
-import qualified Data.ByteString.Lazy as Lazy (ByteString)
-import qualified Data.ByteString.Lazy as Lazy.ByteString
+import qualified Data.ByteString.Lazy_ as Lazy (ByteString)
+import qualified Data.ByteString.Lazy_ as Lazy.ByteString
 import Control.Monad
 import GHC.Base (unsafeChr)
 
diff --git a/lib/Scanner/Internal.hs b/lib/Scanner/Internal.hs
index b2fb829..dd41490 100644
--- a/lib/Scanner/Internal.hs
+++ b/lib/Scanner/Internal.hs
@@ -66,11 +66,13 @@ instance Monad Scanner where
     run s1 bs $ \bs' a ->
       run (s2 a) bs' next
 
+#ifndef __MHS__
 #if !(MIN_VERSION_base(4,13,0))
   {-# INLINE  fail #-}
   fail err = Scanner $ \bs _ ->
     Fail bs err
 #endif
+#endif
 
 instance MonadFail Scanner where
   {-# INLINE  fail #-}
@@ -87,6 +89,7 @@ anyWord8 = Scanner $ \bs next ->
     Just (c, bs') -> next bs' c
     _ -> More $ \bs' -> slowPath bs' next
   where
+  slowPath :: ByteString -> Next Word8 r -> Result r
   slowPath bs next =
     case ByteString.uncons bs of
       Just (c, bs') -> next bs' c
@@ -174,6 +177,7 @@ lookAhead = Scanner $ \bs next ->
     Just (c, _) -> next bs (Just c)
     _ -> More $ \bs' -> slowPath bs' next
   where
+  slowPath :: ByteString -> Next (Maybe Word8) r -> Result r
   slowPath bs next =
     case ByteString.uncons bs of
       Just (c, _) -> next bs (Just c)
diff --git a/portable_hspec/Test/Hspec.hs b/portable_hspec/Test/Hspec.hs
new file mode 100644
index 0000000..e92119b
--- /dev/null
+++ b/portable_hspec/Test/Hspec.hs
@@ -0,0 +1,55 @@
+-- | Portable drop-in replacement of hspec that works both with GHC and MicroHs
+module Test.Hspec
+( Spec
+, hspec
+, describe
+, it
+, shouldBe
+, shouldThrow
+, shouldSatisfy
+, context
+) where
+
+import Data.IORef
+import Control.Monad
+import Control.Exception
+import Control.Monad.IO.Class
+
+type Spec = IO ()
+
+hspec :: Monad m => m a -> m a
+hspec m = m
+
+context :: MonadIO m => String -> m a -> m a
+context name m = do
+  liftIO $ putStrLn "............."
+  liftIO $ putStrLn name
+  m
+
+describe :: MonadIO m => String -> m a -> m a
+describe name m = do
+  liftIO $ putStrLn "-------------"
+  liftIO $ putStrLn name
+  m
+
+it :: MonadIO m => String -> m a -> m a
+it name m = do
+  liftIO $ putStrLn name
+  m
+
+shouldBe :: (MonadIO m, Show a, Eq a) => a -> a -> m ()
+shouldBe a b = unless (a == b) $ do
+  liftIO $ putStrLn $ "FAILED: expected " ++ show b ++ ", but got " ++ show a
+
+shouldSatisfy :: (MonadIO m, Show a) => a -> (a -> Bool) -> m ()
+shouldSatisfy a f = unless (f a) $ do
+  liftIO $ putStrLn $ "FAILED: result does't satisfy the condition: " ++ show a
+
+shouldThrow :: Exception e => IO a -> (e -> Bool) -> IO ()
+shouldThrow m f = do
+  me <- try m
+  case me of
+    Right _ -> putStrLn "FAILED: expected to throw"
+    Left e -> do
+      unless (f e) $ do
+        putStrLn $ "FAILED: exception doesn't satisfy the condition " ++ show e
diff --git a/scanner.cabal b/scanner.cabal
index 6f17d15..1133cba 100644
--- a/scanner.cabal
+++ b/scanner.cabal
@@ -23,6 +23,8 @@ library
                        Scanner.Internal
   other-modules:       Prelude
                        Data.Either
+                       Data.ByteString.Lazy_
+                       GHC.Base
                        Scanner.OctetPredicates
   build-depends:       base <5
                      , fail
@@ -41,6 +43,7 @@ test-suite spec
                      , scanner
   other-modules:       Prelude
                        Data.Either
+                       Data.ByteString.Lazy_
   default-language:    Haskell2010
 
 benchmark bench
diff --git a/spec/spec.hs b/spec/spec.hs
index 1786429..fb2f628 100644
--- a/spec/spec.hs
+++ b/spec/spec.hs
@@ -10,7 +10,7 @@ import Scanner
 import Prelude hiding (take, takeWhile)
 import Data.Either
 import qualified Data.ByteString as ByteString
-import qualified Data.ByteString.Lazy as Lazy.ByteString
+import qualified Data.ByteString.Lazy_ as Lazy.ByteString
 import Test.Hspec
 
 main :: IO ()