diff --git a/maintainers/scripts/haskell/update-cabal2nix-latest.sh b/maintainers/scripts/haskell/update-cabal2nix-latest.sh
index 1f22bb1792f..e8018e1384d 100755
--- a/maintainers/scripts/haskell/update-cabal2nix-latest.sh
+++ b/maintainers/scripts/haskell/update-cabal2nix-latest.sh
@@ -14,4 +14,4 @@ commit="$(jq -r .commit.sha <<< "$head_info")"
 date="$(date "--date=$(jq -r .commit.commit.committer.date <<< "$head_info")" +%F)"
 # generate nix expression from cabal file, replacing the version with the commit date
 echo '# This file defines cabal2nix-latest, used by maintainers/scripts/haskell/regenerate-hackage-packages.sh.' > pkgs/development/haskell-modules/cabal2nix-latest.nix
-cabal2nix "https://github.com/NixOS/cabal2nix/archive/$commit.tar.gz" | sed -e 's/version = ".*"/version = "'"$date"'"/' >> pkgs/development/haskell-modules/cabal2nix-latest.nix
+cabal2nix "https://github.com/NixOS/cabal2nix/archive/$commit.tar.gz" | sed -e 's/version = ".*"/version = "'"unstable-$date"'"/' >> pkgs/development/haskell-modules/cabal2nix-latest.nix
diff --git a/pkgs/development/haskell-modules/cabal2nix-latest.nix b/pkgs/development/haskell-modules/cabal2nix-latest.nix
index 75c9de963a0..a8b37e4e46e 100644
--- a/pkgs/development/haskell-modules/cabal2nix-latest.nix
+++ b/pkgs/development/haskell-modules/cabal2nix-latest.nix
@@ -8,7 +8,7 @@
 }:
 mkDerivation {
   pname = "cabal2nix";
-  version = "2021-05-01";
+  version = "unstable-2021-05-01";
   src = fetchzip {
     url = "https://github.com/NixOS/cabal2nix/archive/849a3507c849e3e2331efbc5ebe391b70a215ddc.tar.gz";
     sha256 = "0g91d2bd72l3kkykc47a2raymvgw6427n7cg9ayzvrpldkd0silc";