diff --git a/Cabal/Language/Haskell/Extension.hs b/Cabal/Language/Haskell/Extension.hs
index 44509d52d75..4a52fe0e959 100644
--- a/Cabal/Language/Haskell/Extension.hs
+++ b/Cabal/Language/Haskell/Extension.hs
@@ -802,6 +802,9 @@ data KnownExtension =
   -- | Enable the use of unboxed sum syntax.
   | UnboxedSums
 
+  -- | Allow use of hexadecimal literal notation for floating-point values.
+  | HexFloatLiterals
+
   deriving (Generic, Show, Read, Eq, Ord, Enum, Bounded, Typeable, Data)
 
 instance Binary KnownExtension
diff --git a/Cabal/changelog b/Cabal/changelog
index d998f01ab4e..d8cc3b74482 100644
--- a/Cabal/changelog
+++ b/Cabal/changelog
@@ -1,6 +1,7 @@
 -*-change-log-*-
 
 2.2.0.0 (current development version)
+	* Add `HexFloatLiterals` to `KnownExtension`
 	* Added `virtual-module` field, to allow modules that are not built
 	  but registered (#4875).
 	* `copyComponent` and `installIncludeFiles` will look for include