diff --git a/LICENSE b/LICENSE
--- a/LICENSE
+++ b/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2009, Henry Bucklow
+Copyright (c) 2009-2016, Henry Bucklow, Charlie Harvey
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
diff --git a/digits.cabal b/digits.cabal
--- a/digits.cabal
+++ b/digits.cabal
@@ -1,19 +1,35 @@
-Build-Type: Custom
+Build-Type: Simple
 Name: digits
 Category: Data
-Version: 0.2
-Cabal-Version: >= 1.2
+Version: 0.3
+Cabal-Version: >= 1.10
 Synopsis: Converts integers to lists of digits and back.
 Description: Converts integers to lists of digits and back.
 License: BSD3
 License-File: LICENSE
-Copyright: (c) 2009 Henry Bucklow
+Copyright: (c) 2009-2016 Henry Bucklow, Charlie Harvey
 Author: Henry Bucklow
 Maintainer: henry@elsie.org.uk
-Tested-With: GHC==6.12
-Build-Depends: base >= 4 && < 5, QuickCheck
-Exposed-Modules: Data.Digits
-Hs-Source-Dirs: src
-Extra-Source-Files: src/Tests.hs
-GHC-Options: -Wall
+Tested-With: GHC==7.10.3
 
+library
+  hs-source-dirs:      src
+  exposed-modules:     Data.Digits
+  build-depends:       base >= 4.7 && < 5
+                     , QuickCheck
+  default-language:    Haskell2010
+
+test-suite digits-test
+  type:                exitcode-stdio-1.0
+  hs-source-dirs:      test
+                     , src
+  main-is:             Tests.hs
+  build-depends:       base
+                     , digits
+                     , QuickCheck
+  ghc-options:         -Wall -threaded -rtsopts -with-rtsopts=-N
+  default-language:    Haskell2010
+
+source-repository head
+  type:     mercurial
+  location: https://bitbucket.org/sffubs/digits
diff --git a/src/Data/Digits.hs b/src/Data/Digits.hs
--- a/src/Data/Digits.hs
+++ b/src/Data/Digits.hs
@@ -1,36 +1,61 @@
-module Data.Digits (digits, digitsRev, unDigits, prop_digitsRoundTrip) where
+module Data.Digits (mDigits, digits, mDigitsRev, digitsRev, unDigits, prop_digitsRoundTrip) where
 
 import Test.QuickCheck
+import Data.Maybe (fromJust)
+import Data.List (genericTake)
 
--- | Returns the digits of a positive integer as a list, in reverse order.
+-- | Returns the digits of a positive integer as a Maybe list, in reverse order
+--   or Nothing if a negative base is given
 --   This is slightly more efficient than in forward order.
-digitsRev :: Integral n
+mDigitsRev :: Integral n
+    => n         -- ^ The base to use.
+    -> n         -- ^ The number to convert to digit form.
+    -> Maybe [n] -- ^ Nothing or Just the digits of the number in list form, in reverse.
+mDigitsRev base i = if base < 0
+                    then Nothing -- We do not support negative bases
+                    else Just $ dr base i
+    where
+      dr _ 0 = []
+      dr b x = case base of
+                0 -> [0]
+                1 -> genericTake x $ repeat 1
+                _ -> let (rest, lastDigit) = quotRem x b
+                     in lastDigit : dr b rest
+
+-- | Returns the digits of a positive integer as a Maybe list.
+--   or Nothing if a negative base is given
+mDigits :: Integral n
     => n -- ^ The base to use.
     -> n -- ^ The number to convert to digit form.
-    -> [n] -- ^ The digits of the number in list form, in reverse.
-digitsRev base i = case i of
-        0 -> []
-        _ -> lastDigit : digitsRev base rest
-    where (rest, lastDigit) = quotRem i base
+    -> Maybe [n] -- ^ Nothing or Just the digits of the number in list form
+mDigits base i = reverse <$> mDigitsRev base i
 
+-- | Returns the digits of a positive integer as a list, in reverse order.
+--   Throws an error if given a negative base.
+digitsRev :: Integral n
+    => n   -- ^ The base to use.
+    -> n   -- ^ The number to convert to digit from.
+    -> [n] -- ^ The digits of the number in list from, in reverse.
+digitsRev base = fromJust . mDigitsRev base
+
 -- | Returns the digits of a positive integer as a list.
+--   Throws an error if given a negative base.
 digits :: Integral n
-    => n -- ^ The base to use (typically 10).
-    -> n -- ^ The number to convert to digit form.
-    -> [n] -- ^ The digits of the number in list form.
+    => n   -- ^ The base to use (typically 10).
+    -> n   -- ^ The number to convert to digit form.
+    -> [n] -- ^ Either Nothing or the digits of the number in list form.
 digits base = reverse . digitsRev base
 
 -- | Takes a list of digits, and converts them back into a positive integer.
 unDigits :: Integral n
-    => n -- ^ The base to use.
+    => n   -- ^ The base to use.
     -> [n] -- ^ The digits of the number in list form.
-    -> n -- ^ The original number.
+    -> n   -- ^ The original number.
 unDigits base = foldl (\ a b -> a * base + b) 0
 
--- | unDigits . digits should be the identity, in any base.
+-- | unDigits . digits should be the identity, in any positive base.
 prop_digitsRoundTrip
     :: Integer -- ^ The integer to test.
     -> Integer -- ^ The base to use.
     -> Property
-prop_digitsRoundTrip i b = i > 0 ==> b > 1 ==> i == (unDigits b . digits b) i
-
+prop_digitsRoundTrip i b = i > 0 ==> b > 0 ==> i == (unDigits b . digits b) i
diff --git a/src/Tests.hs b/src/Tests.hs
deleted file mode 100644
--- a/src/Tests.hs
+++ /dev/null
@@ -1,11 +0,0 @@
-module Main where
-
-import Data.Digits
-import Text.Printf
-import Test.QuickCheck
-
-tests = [
-    ("checkDigitsRoundTrip", quickCheck prop_digitsRoundTrip)]
-
-main = mapM_ (\(s,a) -> printf "%-25s: " s >> a) tests
-
diff --git a/test/Tests.hs b/test/Tests.hs
new file mode 100644
--- /dev/null
+++ b/test/Tests.hs
@@ -0,0 +1,13 @@
+module Main where
+
+import Data.Digits
+import Text.Printf
+import Test.QuickCheck
+
+tests :: [([Char], IO ())]
+tests = [
+    ("checkDigitsRoundTrip", quickCheck prop_digitsRoundTrip)]
+
+main :: IO ()
+main = mapM_ (\(s,a) -> printf "%-25s: " s >> a) tests
+