diff --git a/pkgs/development/haskell-modules/cabal2nix-unstable.nix b/pkgs/development/haskell-modules/cabal2nix-unstable.nix
index a250a7926792..bd88c5e5a0ad 100644
--- a/pkgs/development/haskell-modules/cabal2nix-unstable.nix
+++ b/pkgs/development/haskell-modules/cabal2nix-unstable.nix
@@ -8,10 +8,10 @@
 }:
 mkDerivation {
   pname = "cabal2nix";
-  version = "unstable-2021-06-10";
+  version = "unstable-2021-06-12";
   src = fetchzip {
-    url = "https://github.com/NixOS/cabal2nix/archive/f63eb780e9c946a5037580e29d8b4effa09da905.tar.gz";
-    sha256 = "1xjdghhbryqhm39z1p8z804mcraia33jvfl8v02yfk7q9xk0bpq2";
+    url = "https://github.com/NixOS/cabal2nix/archive/5bb08e994aa17a46676007400794df703c53af58.tar.gz";
+    sha256 = "1cwjmscy3rf64rd7pkkbmp1zri1f6bn46hjnmf6b33jg7wzw11g4";
   };
   isLibrary = true;
   isExecutable = true;
diff --git a/pkgs/top-level/release-haskell.nix b/pkgs/top-level/release-haskell.nix
index 36a5835c9cd0..87a08dddb606 100644
--- a/pkgs/top-level/release-haskell.nix
+++ b/pkgs/top-level/release-haskell.nix
@@ -222,6 +222,7 @@ let
       # working as expected.
       cabal-install = all;
       Cabal_3_4_0_0 = with compilerNames; [ ghc884 ghc8104 ];
+      cabal2nix-unstable = all;
       funcmp = all;
       # Doesn't currently work on ghc-9.0:
       # https://github.com/haskell/haskell-language-server/issues/297