diff --git a/Changelog.md b/Changelog.md
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,5 +1,9 @@
 # Revision history for ipynb
 
+## 0.1.0.1 -- 2020-04-25
+
+* Fixed to build with base64-bytestring 1.1.
+
 ## 0.1.0.0 -- 2019-01-22
 
 * Initial release.
diff --git a/ipynb.cabal b/ipynb.cabal
--- a/ipynb.cabal
+++ b/ipynb.cabal
@@ -1,5 +1,5 @@
 name:                ipynb
-version:             0.1
+version:             0.1.0.1
 synopsis:            Data structure for working with Jupyter notebooks (ipynb).
 description:         ipynb defines a data structure for representing Jupyter
                      notebooks, along with ToJSON and FromJSON instances
diff --git a/src/Data/Ipynb.hs b/src/Data/Ipynb.hs
--- a/src/Data/Ipynb.hs
+++ b/src/Data/Ipynb.hs
@@ -45,6 +45,7 @@
 import Data.Aeson as Aeson
 import qualified Data.Aeson.Types as Aeson
 import Data.ByteString (ByteString)
+import qualified Data.ByteString as B
 import qualified Data.ByteString.Base64 as Base64
 import Data.Char (isSpace)
 import qualified Data.HashMap.Strict as HM
@@ -483,10 +484,22 @@
 instance ToJSON MimeBundle where
   toJSON (MimeBundle m) =
     let mimeBundleToValue (BinaryData bs) =
-          toJSON $ TE.decodeUtf8 . Base64.joinWith "\n" 76 . Base64.encode $ bs
+          toJSON .
+            TE.decodeUtf8 .
+            (<> "\n") .
+            B.intercalate "\n" .  chunksOf 76 .
+            Base64.encode
+            $ bs
         mimeBundleToValue (JsonData v) = v
         mimeBundleToValue (TextualData t) = toJSON (breakLines t)
     in  toJSON $ M.map mimeBundleToValue m
+
+chunksOf :: Int -> ByteString -> [ByteString]
+chunksOf k s
+   | B.null s = []
+   | otherwise =
+     let (h,t) = B.splitAt k s
+     in h : chunksOf k t
 
 -- | Break up a string into a list of strings, each representing
 -- one line of the string (including trailing newline if any).
diff --git a/test/roundtrip.hs b/test/roundtrip.hs
--- a/test/roundtrip.hs
+++ b/test/roundtrip.hs
@@ -2,9 +2,10 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 
 import Data.Aeson (Value (..), eitherDecode, encode)
-import Data.Aeson.Diff
+import Data.Aeson.Diff as AesonDiff
 import qualified Data.ByteString.Base64 as Base64
 import qualified Data.ByteString.Lazy as BL
+import qualified Data.ByteString as B
 import qualified Data.HashMap.Strict as HM
 import Data.Ipynb
 import qualified Data.Text as T
@@ -16,6 +17,7 @@
 import System.FilePath
 import Test.Tasty
 import Test.Tasty.HUnit
+import Data.Monoid
 
 main :: IO ()
 main = do
@@ -49,9 +51,18 @@
        case Base64.decode (TE.encodeUtf8 (T.filter (/='\n') t)) of
             Left _  -> String t  -- textual
             Right b -> String $
-              TE.decodeUtf8 . Base64.joinWith "\n" 76 . Base64.encode $ b
+              TE.decodeUtf8 .  (<> "\n") .
+              B.intercalate "\n" .  chunksOf 76 .
+              Base64.encode $ b
      go v = v
 
+chunksOf :: Int -> B.ByteString -> [B.ByteString]
+chunksOf k s
+   | B.null s = []
+   | otherwise =
+     let (h,t) = B.splitAt k s
+     in h : chunksOf k t
+
 rtTest :: FilePath -> TestTree
 rtTest fp = testCase fp $ do
   inRaw <- BL.readFile fp
@@ -68,7 +79,8 @@
   (nb' :: Notebook NbV3) <- either error return $ eitherDecode outRaw
   (outJSON :: Value) <- either error return $ eitherDecode outRaw
   -- test that (read . write) == id
-  let patch' = diff (normalizeBase64 inJSON) (normalizeBase64 outJSON)
+  let patch' = AesonDiff.diff
+         (normalizeBase64 inJSON) (normalizeBase64 outJSON)
   assertBool (show patch') (patch' == Patch [])
   -- now test that (write . read) == id
   assertEqual "write . read != read" nb nb'
@@ -81,7 +93,8 @@
   (nb' :: Notebook NbV4) <- either error return $ eitherDecode outRaw
   (outJSON :: Value) <- either error return $ eitherDecode outRaw
   -- test that (read . write) == id
-  let patch' = diff (normalizeBase64 inJSON) (normalizeBase64 outJSON)
+  let patch' = AesonDiff.diff
+       (normalizeBase64 inJSON) (normalizeBase64 outJSON)
   assertBool (show patch') (patch' == Patch [])
   -- now test that (write . read) == id
   assertEqual "write . read != read" nb nb'