diff --git a/Math/NumberTheory/Roots/General.hs b/Math/NumberTheory/Roots/General.hs
--- a/Math/NumberTheory/Roots/General.hs
+++ b/Math/NumberTheory/Roots/General.hs
@@ -23,8 +23,10 @@
 
 #include "MachDeps.h"
 
+import Prelude hiding (Foldable(..))
 import Data.Bits (countTrailingZeros, shiftL, shiftR)
-import Data.List (foldl', sortBy)
+import Data.Foldable (Foldable(..))
+import Data.List (sortBy)
 import Data.Maybe (isJust)
 import GHC.Exts (Int(..), Word(..), word2Int#, int2Double#, double2Int#, isTrue#, Ptr(..), indexWord16OffAddr#, (/##), (**##))
 #if MIN_VERSION_base(4,16,0)
diff --git a/Math/NumberTheory/Roots/Squares.hs b/Math/NumberTheory/Roots/Squares.hs
--- a/Math/NumberTheory/Roots/Squares.hs
+++ b/Math/NumberTheory/Roots/Squares.hs
@@ -57,6 +57,7 @@
 "integerSquareRoot'/Int"     integerSquareRoot' = isqrtInt'
 "integerSquareRoot'/Word"    integerSquareRoot' = isqrtWord
 "integerSquareRoot'/Integer" integerSquareRoot' = isqrtInteger
+"integerSquareRoot'/Natural" integerSquareRoot' = fromInteger . isqrtInteger . toInteger
   #-}
 {-# INLINE [1] integerSquareRoot' #-}
 integerSquareRoot' :: Integral a => a -> a
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -7,14 +7,14 @@
 The [integer square root](https://en.wikipedia.org/wiki/Integer_square_root)
 (`integerSquareRoot`)
 of a non-negative integer
-_n_
+$n$
 is the greatest integer
-_m_
+$m$
 such that
-<img src="https://render.githubusercontent.com/render/math?math=m\le\sqrt{n}">.
+$m\le\sqrt{n}$.
 Alternatively, in terms of the
 [floor function](https://en.wikipedia.org/wiki/Floor_and_ceiling_functions),
-<img src="https://render.githubusercontent.com/render/math?math=m = \lfloor\sqrt{n}\rfloor">.
+$m = \lfloor\sqrt{n}\rfloor$.
 
 For example,
 
@@ -57,9 +57,9 @@
 The integer cube root
 (`integerCubeRoot`)
 of an integer
-_n_
+$n$
 equals to
-<img src="https://render.githubusercontent.com/render/math?math=\lfloor\sqrt[3]{n}\rfloor">.
+$\lfloor\sqrt[3]{n}\rfloor$.
 
 Again, a naive approach is to implement `integerCubeRoot`
 via `Double`-typed computations:
@@ -88,7 +88,7 @@
 In spirit of `integerSquareRoot` and `integerCubeRoot` this library
 covers the general case as well, providing
 `integerRoot :: (Integral a, Integral b) => b -> a -> a`
-to compute integer _k_-th roots of arbitrary precision.
+to compute integer $k$-th roots of arbitrary precision.
 
 There is also `highestPower` routine, which tries hard to represent
 its input as a power with as large exponent as possible. This is a useful function
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,7 @@
+# 1.0.3.0
+
+* Add a rewrite rule for `integerSquareRoot` of `Natural`.
+
 # 1.0.2.0
 
 * More fixes for big-endian architectures.
diff --git a/integer-roots.cabal b/integer-roots.cabal
--- a/integer-roots.cabal
+++ b/integer-roots.cabal
@@ -1,5 +1,5 @@
 name:          integer-roots
-version:       1.0.2.0
+version:       1.0.3.0
 cabal-version: >=1.10
 build-type:    Simple
 license:       MIT
@@ -12,7 +12,7 @@
 description:   Calculating integer roots and testing perfect powers of arbitrary precision. Originally part of <https://hackage.haskell.org/package/arithmoi arithmoi> package.
 category:      Math, Algorithms, Number Theory
 author:        Daniel Fischer, Andrew Lelechenko
-tested-with:   GHC ==8.0.2 GHC ==8.2.2 GHC ==8.4.4 GHC ==8.6.5 GHC ==8.8.4 GHC ==8.10.7 GHC ==9.0.1 GHC ==9.2.1
+tested-with:   GHC ==8.0.2 GHC ==8.2.2 GHC ==8.4.4 GHC ==8.6.5 GHC ==8.8.4 GHC ==8.10.7 GHC ==9.0.2 GHC ==9.2.8 GHC ==9.4.8 GHC ==9.6.7 GHC ==9.8.4 GHC ==9.10.2 GHC ==9.12.2
 extra-source-files:
   changelog.md
   README.md
@@ -27,7 +27,7 @@
   if impl(ghc < 9.0)
     build-depends: integer-gmp <1.2
   else
-    build-depends: ghc-bignum < 1.3
+    build-depends: ghc-bignum < 1.4
   exposed-modules:
     Math.NumberTheory.Roots
   other-modules:
@@ -49,7 +49,7 @@
     smallcheck >=1.2 && <1.3,
     tasty >=0.10,
     tasty-hunit >=0.9 && <0.11,
-    tasty-quickcheck >=0.9 && <0.11,
+    tasty-quickcheck >=0.9 && <0.12,
     tasty-smallcheck >=0.8 && <0.9
   other-modules:
     Math.NumberTheory.Roots.CubesTests
@@ -63,12 +63,3 @@
   default-language: Haskell2010
   hs-source-dirs: test-suite
   ghc-options: -Wall -Widentities -Wcompat
-
-test-suite integer-roots-doctests
-  type: exitcode-stdio-1.0
-  main-is: Doctest.hs
-  hs-source-dirs: test-suite
-  build-depends:
-    base,
-    doctest >= 0.8
-  default-language: Haskell2010
diff --git a/test-suite/Doctest.hs b/test-suite/Doctest.hs
deleted file mode 100644
--- a/test-suite/Doctest.hs
+++ /dev/null
@@ -1,4 +0,0 @@
-import Test.DocTest
-
-main :: IO ()
-main = doctest ["Math/NumberTheory/Roots.hs"]
diff --git a/test-suite/Math/NumberTheory/Roots/GeneralTests.hs b/test-suite/Math/NumberTheory/Roots/GeneralTests.hs
--- a/test-suite/Math/NumberTheory/Roots/GeneralTests.hs
+++ b/test-suite/Math/NumberTheory/Roots/GeneralTests.hs
@@ -13,6 +13,7 @@
   ( testSuite
   ) where
 
+import Data.Bits
 import Test.Tasty
 import Test.Tasty.HUnit
 import Test.Tasty.QuickCheck as QC
@@ -90,9 +91,9 @@
       , 3
       , 2)
 
-  , a ( -2 ^ 63 :: Int
+  , a ( minBound :: Int
       , -2 :: Int
-      , 63)
+      , fromIntegral (finiteBitSize (0 :: Int) - 1))
 
   , a ( (2 ^ 63 - 1) ^ 21
       , 2 ^ 63 - 1