diff --git a/CHANGES.md b/CHANGES.md
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,7 @@
+# 1.5.1 (October 2023)
+
+* Require building with `versions >= 6.0.2`.
+
 # 1.5 (July 2023)
 
 * Allow building with GHC 9.6.
diff --git a/src/What4/Utils/Versions.hs b/src/What4/Utils/Versions.hs
--- a/src/What4/Utils/Versions.hs
+++ b/src/What4/Utils/Versions.hs
@@ -3,8 +3,6 @@
 {-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE TemplateHaskell #-}
 
-{-# OPTIONS_GHC -Wno-orphans #-}
-
 module What4.Utils.Versions where
 
 import qualified Config as Config
@@ -20,10 +18,6 @@
 
 import           Language.Haskell.TH
 import           Language.Haskell.TH.Lift
-
--- NB, orphan instances :-(
-deriving instance Lift Versions.VUnit
-deriving instance Lift Versions.Version
 
 ver :: Text -> Q Exp
 ver nm =
diff --git a/what4.cabal b/what4.cabal
--- a/what4.cabal
+++ b/what4.cabal
@@ -1,6 +1,6 @@
 Cabal-version: 2.4
 Name:          what4
-Version:       1.5
+Version:       1.5.1
 Author:        Galois Inc.
 Maintainer:    rscott@galois.com, kquick@galois.com
 Copyright:     (c) Galois, Inc 2014-2023
@@ -135,7 +135,7 @@
     unordered-containers >= 0.2.10,
     utf8-string >= 1.0.1,
     vector >= 0.12.1,
-    versions >= 4.0 && < 6.0,
+    versions >= 6.0.2 && < 6.1,
     zenc >= 0.1.0 && < 0.2.0,
     ghc-prim >= 0.5.2