diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,13 @@
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## 0.6.1
+### Added
+- Compatibility with latest GHC and base.
+
+### Changed
+- Update minimum base to 4.9.
+
 ## 0.6.0
 ### Changed
 - Force initialization of addresses through smart constructor.
diff --git a/haskoin-core.cabal b/haskoin-core.cabal
--- a/haskoin-core.cabal
+++ b/haskoin-core.cabal
@@ -2,10 +2,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 60cf3a9fd398cb3bffeaa6d67b67e5bf4d56163b98c4137d7738ace0286ec13f
+-- hash: a15368965c6befac912e285d4519667d835f4c9330b283af73a732d62915c260
 
 name:           haskoin-core
-version:        0.6.0
+version:        0.6.1
 synopsis:       Bitcoin & Bitcoin Cash library for Haskell
 description:    Haskoin Core is a complete Bitcoin and Bitcoin Cash library of functions and data types for Haskell developers.
 category:       Bitcoin, Finance, Network
@@ -81,7 +81,7 @@
       QuickCheck
     , aeson
     , array
-    , base >=4.7 && <5
+    , base >=4.9 && <5
     , base16-bytestring
     , bytestring
     , cereal
@@ -131,7 +131,7 @@
       HUnit
     , QuickCheck
     , aeson
-    , base >=4.7 && <5
+    , base >=4.9 && <5
     , bytestring
     , cereal
     , containers
diff --git a/src/Network/Haskoin/Block/Headers.hs b/src/Network/Haskoin/Block/Headers.hs
--- a/src/Network/Haskoin/Block/Headers.hs
+++ b/src/Network/Haskoin/Block/Headers.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE FlexibleContexts  #-}
 {-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE LambdaCase        #-}
 {-# LANGUAGE RecordWildCards   #-}
 {-|
 Module      : Network.Haskoin.Block.Headers
@@ -278,11 +279,13 @@
                 (MaybeT (parentBlock bh))
         pars <- lift $ getParents 10 par
         bb <- lift getBestBlockHeader
-        bns@(bn:_) <- go par [] bb par pars bhs
-        lift $ addBlockHeaders bns
-        let bb' = chooseBest bn bb
-        when (bb' /= bb) $ lift $ setBestBlockHeader bb'
-        return bns
+        go par [] bb par pars bhs >>= \case
+            bns@(bn:_) -> do
+                lift $ addBlockHeaders bns
+                let bb' = chooseBest bn bb
+                when (bb' /= bb) $ lift $ setBestBlockHeader bb'
+                return bns
+            _ -> undefined
   where
     chained (h1:h2:hs) = headerHash h1 == prevBlock h2 && chained (h2 : hs)
     chained _          = True
diff --git a/src/Network/Haskoin/Test/Script.hs b/src/Network/Haskoin/Test/Script.hs
--- a/src/Network/Haskoin/Test/Script.hs
+++ b/src/Network/Haskoin/Test/Script.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE LambdaCase #-}
 {-|
 Module      : Network.Haskoin.Test.Script
 Copyright   : No rights reserved
@@ -189,10 +190,10 @@
 -- private key.
 arbitraryTxSignature :: Network -> Gen (TxHash, SecKey, TxSignature)
 arbitraryTxSignature net = do
-    (msg, key, sig) <- arbitrarySignature
+    (m, key, sig) <- arbitrarySignature
     sh <- (fromIntegral <$> (arbitrary :: Gen Word8)) `suchThat` filterBad
     let txsig = TxSignature sig sh
-    return (TxHash msg, key, txsig)
+    return (TxHash m, key, txsig)
   where
     filterBad sh = not $
         isSigHashUnknown sh ||
@@ -338,29 +339,37 @@
 -- | Arbitrary 'ScriptInput' of type 'ScriptHashInput' containing a
 -- 'RedeemScript' of type 'PayMulSig' and an input of type 'SpendMulSig'.
 arbitraryMulSigSHInput :: Network -> Gen ScriptInput
-arbitraryMulSigSHInput net = do
-    rdm@(PayMulSig _ m) <- arbitraryMSOutput
-    sigs <- vectorOf m (arbitraryTxSignatureEmpty net)
-    return $ ScriptHashInput (SpendMulSig sigs) rdm
+arbitraryMulSigSHInput net =
+    arbitraryMSOutput >>= \case
+        rdm@(PayMulSig _ m) -> do
+            sigs <- vectorOf m (arbitraryTxSignatureEmpty net)
+            return $ ScriptHashInput (SpendMulSig sigs) rdm
+        _ -> undefined
 
 -- | Arbitrary 'ScriptInput' of type 'ScriptHashInput' containing a
 -- 'RedeemScript' of type 'PayMulSig' and an input of type 'SpendMulSig'.
 arbitraryMulSigSHInputC :: Network -> Gen ScriptInput
-arbitraryMulSigSHInputC net = do
-    rdm@(PayMulSig _ m) <- arbitraryMSOutputC
-    sigs <- vectorOf m (arbitraryTxSignatureEmpty net)
-    return $ ScriptHashInput (SpendMulSig sigs) rdm
+arbitraryMulSigSHInputC net =
+    arbitraryMSOutputC >>= \case
+        rdm@(PayMulSig _ m) -> do
+          sigs <- vectorOf m (arbitraryTxSignatureEmpty net)
+          return $ ScriptHashInput (SpendMulSig sigs) rdm
+        _ -> undefined
 
 -- | Like 'arbitraryMulSigSHCInput' with no empty signatures.
 arbitraryMulSigSHInputFull :: Network -> Gen ScriptInput
-arbitraryMulSigSHInputFull net = do
-    rdm@(PayMulSig _ m) <- arbitraryMSOutput
-    sigs <- map lst3 <$> vectorOf m (arbitraryTxSignature net)
-    return $ ScriptHashInput (SpendMulSig sigs) rdm
+arbitraryMulSigSHInputFull net =
+    arbitraryMSOutput >>= \case
+        rdm@(PayMulSig _ m) -> do
+            sigs <- map lst3 <$> vectorOf m (arbitraryTxSignature net)
+            return $ ScriptHashInput (SpendMulSig sigs) rdm
+        _ -> undefined
 
 -- | Like 'arbitraryMulSigSHCInput' with no empty signatures.
 arbitraryMulSigSHInputFullC :: Network -> Gen ScriptInput
-arbitraryMulSigSHInputFullC net = do
-    rdm@(PayMulSig _ m) <- arbitraryMSOutputC
-    sigs <- map lst3 <$> vectorOf m (arbitraryTxSignature net)
-    return $ ScriptHashInput (SpendMulSig sigs) rdm
+arbitraryMulSigSHInputFullC net =
+    arbitraryMSOutputC >>= \case
+        rdm@(PayMulSig _ m) -> do
+            sigs <- map lst3 <$> vectorOf m (arbitraryTxSignature net)
+            return $ ScriptHashInput (SpendMulSig sigs) rdm
+        _ -> undefined
diff --git a/test/Network/Haskoin/BlockSpec.hs b/test/Network/Haskoin/BlockSpec.hs
--- a/test/Network/Haskoin/BlockSpec.hs
+++ b/test/Network/Haskoin/BlockSpec.hs
@@ -5,7 +5,6 @@
 
 import           Control.Monad.State.Strict
 import           Data.Aeson                    as A
-import           Data.ByteString               (ByteString)
 import           Data.Either                   (fromRight)
 import           Data.Map.Strict               (singleton)
 import           Data.Maybe                    (fromJust)
@@ -47,8 +46,7 @@
                         getBestBlockHeader
              in nodeHeight bb `shouldBe` 100
         it "builds a block locator" $
-            let net = bchRegTest
-                loc =
+            let loc =
                     withChain net $ do
                         chain net (getGenesisHeader net) 100
                         bb <- getBestBlockHeader
@@ -68,21 +66,19 @@
             forAll arbitraryBlockHash $ \h ->
                 fromString (cs $ blockHashToHex h) == h
         it "show and read block hash" $
-            property $
-            forAll arbitraryBlockHash $ \h ->
-                read (show h) == h
+            property $ forAll arbitraryBlockHash $ \h -> read (show h) == h
         it "json block hash" $ property $ forAll arbitraryBlockHash testID
     describe "merkle trees" $ do
-        let net = btc
+        let net' = btc
         it "builds tree of right width at height 1" $ property testTreeWidth
         it "builds tree of right width at height 0" $ property testBaseWidth
         it "builds and extracts partial merkle tree" $
             property $
             forAll
                 (listOf1 ((,) <$> arbitraryTxHash <*> arbitrary))
-                (buildExtractTree net)
+                (buildExtractTree net')
         it "merkle root test vectors" $
-            zipWithM_ (curry mapMerkleVectors) merkleVectors [0 ..]
+            mapM_ runMerkleVector merkleVectors
     describe "compact number" $ do
         it "compact number local vectors" testCompact
         it "compact number imported vectors" testCompactBitcoinCore
@@ -244,9 +240,6 @@
     assertBool
         "vector 9 (decode) (positive)"
         ((> 0) . fst $ decodeCompact 0xff123456)
-
-mapMerkleVectors :: ((Text, [Text]), Int) -> Assertion
-mapMerkleVectors (v, i) = runMerkleVector v
 
 runMerkleVector :: (Text, [Text]) -> Assertion
 runMerkleVector (r, hs) =