diff --git a/HaskellNet.cabal b/HaskellNet.cabal
index 88f6c60..f623d11 100644
--- a/HaskellNet.cabal
+++ b/HaskellNet.cabal
@@ -68,7 +68,7 @@ Library
     Network.Mail.Mime
 
   Build-Depends:
-    base >= 4.3 && < 4.17,
+    base >= 4.3 && < 4.18,
     network >= 2.6.3.1 && < 3.2,
     mtl,
     bytestring >=0.10.2,
diff --git a/cabal.project b/cabal.project
new file mode 100644
index 0000000..1b8a75e
--- /dev/null
+++ b/cabal.project
@@ -0,0 +1,2 @@
+packages:
+    .
diff --git a/src/Network/HaskellNet/Auth.hs b/src/Network/HaskellNet/Auth.hs
index a0874fd..c889c85 100644
--- a/src/Network/HaskellNet/Auth.hs
+++ b/src/Network/HaskellNet/Auth.hs
@@ -1,9 +1,15 @@
+{-# language CPP #-}
+
 module Network.HaskellNet.Auth
 where
 
 import Crypto.Hash.MD5
 import Data.Text.Encoding.Base64 as B64
 
+#if MIN_VERSION_base64(0,5,0)
+import Data.Base64.Types as B64
+#endif
+
 import Data.Word
 import Data.List
 import Data.Bits
@@ -28,10 +34,24 @@ instance Show AuthType where
               showMain CRAM_MD5 = "CRAM-MD5"
 
 b64Encode :: String -> String
-b64Encode = T.unpack . B64.encodeBase64 . T.pack
+b64Encode = T.unpack . encode . T.pack
+    where encode =
+#if MIN_VERSION_base64(0,5,0)
+              B64.extractBase64 . B64.encodeBase64
+#else
+              B64.encodeBase64
+#endif
+
+
 
 b64Decode :: String -> String
-b64Decode = T.unpack . B64.decodeBase64Lenient . T.pack
+b64Decode = T.unpack . decode . T.pack
+    where decode =
+#if MIN_VERSION_base64(0,5,0)
+              B64.decodeBase64Lenient . B64.assertBase64
+#else
+              B64.decodeBase64Lenient
+#endif
 
 showOctet :: [Word8] -> String
 showOctet = concatMap hexChars