diff --git a/opentheory-bits.cabal b/opentheory-bits.cabal
--- a/opentheory-bits.cabal
+++ b/opentheory-bits.cabal
@@ -1,5 +1,5 @@
 name: opentheory-bits
-version: 1.63
+version: 1.64
 category: Formal Methods
 synopsis: Natural number to bit-list conversions
 license: MIT
@@ -10,20 +10,17 @@
 maintainer: Joe Leslie-Hurd <joe@gilith.com>
 description:
   Natural number to bit-list conversions - this package was automatically
-  generated from the OpenTheory package natural-bits-1.63
+  generated from the OpenTheory package natural-bits-1.64
 
 library
   build-depends:
     base >= 4.0 && < 5.0,
     QuickCheck >= 2.4.0.1 && < 3.0,
-    opentheory-primitive >= 1.3 && < 2.0,
-    opentheory >= 1.195 && < 1.196,
-    opentheory-probability >= 1.46 && < 1.47
-
+    opentheory-primitive >= 1.4 && < 2.0,
+    opentheory >= 1.195 && < 1.197,
+    opentheory-probability >= 1.46 && < 1.48
   hs-source-dirs: src
-
   ghc-options: -Wall
-
   exposed-modules:
-    OpenTheory.Natural.Bits
+    OpenTheory.Natural.Bits,
     OpenTheory.Natural.Uniform
diff --git a/src/OpenTheory/Natural/Bits.hs b/src/OpenTheory/Natural/Bits.hs
--- a/src/OpenTheory/Natural/Bits.hs
+++ b/src/OpenTheory/Natural/Bits.hs
@@ -26,29 +26,20 @@
 headBits :: Primitive.Natural.Natural -> Bool
 headBits n = Natural.naturalOdd n
 
-shiftRight ::
-  Primitive.Natural.Natural -> Primitive.Natural.Natural ->
-    Primitive.Natural.Natural
-shiftRight n k = n `div` 2 ^ k
-
 bit :: Primitive.Natural.Natural -> Primitive.Natural.Natural -> Bool
-bit n i = headBits (shiftRight n i)
+bit n i = headBits (Primitive.Natural.shiftRight n i)
 
 bound ::
   Primitive.Natural.Natural -> Primitive.Natural.Natural ->
     Primitive.Natural.Natural
-bound n k = n `mod` 2 ^ k
+bound n k =
+  n - Primitive.Natural.shiftLeft (Primitive.Natural.shiftRight n k) k
 
 fromList :: [Bool] -> Primitive.Natural.Natural
 fromList l = append l 0
 
-shiftLeft ::
-  Primitive.Natural.Natural -> Primitive.Natural.Natural ->
-    Primitive.Natural.Natural
-shiftLeft n k = 2 ^ k * n
-
 tailBits :: Primitive.Natural.Natural -> Primitive.Natural.Natural
-tailBits n = n `div` 2
+tailBits n = Primitive.Natural.shiftRight n 1
 
 toList :: Primitive.Natural.Natural -> [Bool]
 toList n = if n == 0 then [] else headBits n : toList (tailBits n)