diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,6 @@
+# 0.4.2 [2018.09.18]
+* Allow `singletons-2.5`.
+
 # 0.4.1 [2018.05.02]
 * Add a `Num Nat` instance.
 * Implement `signum` in the `PNum`/`SNum` instances for `Nat`.
diff --git a/Data/Nat.hs b/Data/Nat.hs
--- a/Data/Nat.hs
+++ b/Data/Nat.hs
@@ -4,6 +4,9 @@
   InstanceSigs, TypeOperators, PolyKinds, StandaloneDeriving,
   FlexibleContexts, AllowAmbiguousTypes, CPP, OverloadedStrings,
   EmptyCase #-}
+#if __GLASGOW_HASKELL__ >= 806
+{-# LANGUAGE QuantifiedConstraints #-}
+#endif
 
 module Data.Nat (
     Nat(..)
diff --git a/singleton-nats.cabal b/singleton-nats.cabal
--- a/singleton-nats.cabal
+++ b/singleton-nats.cabal
@@ -1,5 +1,5 @@
 name:                singleton-nats
-version:             0.4.1
+version:             0.4.2
 synopsis:            Unary natural numbers relying on the singletons infrastructure.
 description:         Unary natural number relying on the <https://hackage.haskell.org/package/singletons singletons> infrastructure. More information about the general usage of singletons can be found on the <https://github.com/goldfirere/singletons singletons github> page.
 category:            Data, Dependent Types
@@ -13,7 +13,7 @@
 
 build-type:          Simple
 cabal-version:       >=1.10
-tested-with:         GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.2
+tested-with:         GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.3, GHC == 8.6.1
 extra-source-files:  CHANGELOG.md, README.md
 
 source-repository head
@@ -26,7 +26,7 @@
 
   build-depends:
     base >=4.8.1.0 && <5,
-    singletons >= 2.2 && < 2.5
+    singletons >= 2.2 && < 2.6
 
   default-language:    Haskell2010
   ghc-options:         -Wall -Wno-unticked-promoted-constructors