diff --git a/src/Data/Color/Internal.hs b/src/Data/Color/Internal.hs
--- a/src/Data/Color/Internal.hs
+++ b/src/Data/Color/Internal.hs
@@ -152,8 +152,9 @@
 		fromIntegral $ r `shiftR` 23,
 		fromIntegral $ g `shiftR` 23,
 		fromIntegral $ b `shiftR` 23 )
-	RgbDouble_ r g b ->
-		let [r', g', b'] = cDoubleToWord8 <$> [r, g, b] in (r', g', b')
+	RgbDouble_ r g b -> case cDoubleToWord8 <$> [r, g, b] of
+		[r', g', b'] -> (r', g', b')
+		_ -> error "never occur"
 
 {-# COMPLETE RgbWord16 #-}
 
@@ -616,8 +617,9 @@
 unPremultipliedDouble :: (Eq d, Fractional d) => (d, d, d, d) -> [d]
 unPremultipliedDouble (r, g, b, a) = [r ./. a, g ./. a, b ./. a, a]
 
-div' :: Integral n => n -> n -> n
+div' :: (Integral n, Bounded n) => n -> n -> n
 0 `div'` 0 = 0
+_ `div'` 0 = maxBound
 a `div'` b = a `div` b
 
 (./.) :: (Eq a, Fractional a) => a -> a -> a
diff --git a/union-color.cabal b/union-color.cabal
--- a/union-color.cabal
+++ b/union-color.cabal
@@ -1,11 +1,11 @@
 cabal-version: 1.12
 
--- This file has been generated from package.yaml by hpack version 0.34.4.
+-- This file has been generated from package.yaml by hpack version 0.35.2.
 --
 -- see: https://github.com/sol/hpack
 
 name:           union-color
-version:        0.1.2.0
+version:        0.1.2.1
 synopsis:       Unify verious color formats
 description:    Please see the README on GitHub at <https://github.com/YoshikuniJujo/union-color#readme>
 category:       data, graphics
