diff --git a/Data/Mod.hs b/Data/Mod.hs
--- a/Data/Mod.hs
+++ b/Data/Mod.hs
@@ -108,7 +108,7 @@
 
 bigNatToNat :: BigNat -> Natural
 bigNatToNat r# =
-  if isTrue# (sizeofBigNat# r# ==# 1#) then NatS# (bigNatToWord r#) else NatJ# r#
+  if isTrue# (sizeofBigNat# r# <=# 1#) then NatS# (bigNatToWord r#) else NatJ# r#
 
 subIfGe :: BigNat -> BigNat -> Natural
 subIfGe z# m# = case z# `compareBigNat` m# of
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# mod [![Build Status](https://travis-ci.org/Bodigrim/mod.svg)](https://travis-ci.org/Bodigrim/mod) [![Hackage](http://img.shields.io/hackage/v/mod.svg)](https://hackage.haskell.org/package/mod) [![Hackage CI](https://matrix.hackage.haskell.org/api/v2/packages/mod/badge)](https://matrix.hackage.haskell.org/package/mod) [![Stackage LTS](http://stackage.org/package/mod/badge/lts)](http://stackage.org/lts/package/mod) [![Stackage Nightly](http://stackage.org/package/mod/badge/nightly)](http://stackage.org/nightly/package/mod)
+# mod [![Build Status](https://github.com/Bodigrim/mod/workflows/Haskell-CI/badge.svg)](https://github.com/Bodigrim/mod/actions?query=workflow%3AHaskell-CI) [![Hackage](http://img.shields.io/hackage/v/mod.svg)](https://hackage.haskell.org/package/mod) [![Hackage CI](https://matrix.hackage.haskell.org/api/v2/packages/mod/badge)](https://matrix.hackage.haskell.org/package/mod) [![Stackage LTS](http://stackage.org/package/mod/badge/lts)](http://stackage.org/lts/package/mod) [![Stackage Nightly](http://stackage.org/package/mod/badge/nightly)](http://stackage.org/nightly/package/mod)
 
 [Modular arithmetic](https://en.wikipedia.org/wiki/Modular_arithmetic),
 promoting moduli to the type level, with an emphasis on performance.
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,7 @@
+# 0.1.2.1
+
+* Support `integer-gmp-1.1`.
+
 # 0.1.2.0
 
 * Add `Storable`, `Prim` and `Unbox` instances.
diff --git a/mod.cabal b/mod.cabal
--- a/mod.cabal
+++ b/mod.cabal
@@ -1,5 +1,5 @@
 name:          mod
-version:       0.1.2.0
+version:       0.1.2.1
 cabal-version: >=1.10
 build-type:    Simple
 license:       MIT
@@ -36,7 +36,7 @@
   build-depends:
     base >=4.10 && <5,
     deepseq,
-    integer-gmp <1.1
+    integer-gmp <1.2
   if flag(semirings)
     build-depends:
       semirings >= 0.5
@@ -48,7 +48,7 @@
     Data.Mod
     Data.Mod.Word
   default-language: Haskell2010
-  ghc-options: -Wall -O2
+  ghc-options: -Wall -O2 -Wno-deprecations
 
 test-suite mod-tests
   build-depends: