diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## [0.5.0.4] - 2020-06-17
+
+### Added
+
+* `distinctOrd`
+
 ## [0.5.0.3] - 2020-04-23
 
 ### Changed
diff --git a/src/Data/Validity/Set.hs b/src/Data/Validity/Set.hs
--- a/src/Data/Validity/Set.hs
+++ b/src/Data/Validity/Set.hs
@@ -1,17 +1,22 @@
+{-# LANGUAGE CPP #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 
 module Data.Validity.Set where
 
-import Data.Validity
-
+import Data.Containers.ListUtils
 import Data.Set (Set)
 import qualified Data.Set as S
+import Data.Validity
 
 -- | A 'Set' of things is valid if all the elements are valid and the 'Set' itself
 -- is valid.
 instance (Ord v, Validity v) => Validity (Set v) where
-    validate s =
-        mconcat
-            [ declare "The set structure is valid." $ S.valid s
-            , annotate (S.toList s) "Set elements"
-            ]
+  validate s =
+    mconcat
+      [ declare "The set structure is valid." $ S.valid s,
+        annotate (S.toList s) "Set elements"
+      ]
+#if MIN_VERSION_containers(0,6,0)
+distinctOrd :: Ord a => [a] -> Bool
+distinctOrd ls = nubOrd ls == ls
+#endif
diff --git a/validity-containers.cabal b/validity-containers.cabal
--- a/validity-containers.cabal
+++ b/validity-containers.cabal
@@ -4,10 +4,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 3adf3a60a7a251b920837101acdb564502883371a5b6ba8f41c32dafe926f0ff
+-- hash: 2e970343bc40866f2768fe78bd9427b658402d4bf787b23ad793a1cae658a82f
 
 name:           validity-containers
-version:        0.5.0.3
+version:        0.5.0.4
 synopsis:       Validity instances for containers
 category:       Validity
 homepage:       https://github.com/NorfairKing/validity#readme
@@ -38,6 +38,6 @@
       src
   build-depends:
       base >=4.7 && <5
-    , containers
+    , containers >=0.6.0.1
     , validity >=0.5
   default-language: Haskell2010