diff --git a/pkgs/development/haskell-modules/configuration-nix.nix b/pkgs/development/haskell-modules/configuration-nix.nix
index b1d73cf8019f..7100aeeb7fde 100644
--- a/pkgs/development/haskell-modules/configuration-nix.nix
+++ b/pkgs/development/haskell-modules/configuration-nix.nix
@@ -868,9 +868,9 @@ self: super: builtins.intersectAttrs super {
 
   cachix = generateOptparseApplicativeCompletion "cachix" (super.cachix.override { nix = pkgs.nixVersions.nix_2_7; });
 
-  hercules-ci-agent = appendConfigureFlag "-fnix-2_4" (super.hercules-ci-agent.override { nix = pkgs.nixVersions.nix_2_7; });
-  hercules-ci-cnix-expr = appendConfigureFlag "-fnix-2_4" (super.hercules-ci-cnix-expr.override { nix = pkgs.nixVersions.nix_2_7; });
-  hercules-ci-cnix-store = appendConfigureFlag "-fnix-2_4" (super.hercules-ci-cnix-store.override { nix = pkgs.nixVersions.nix_2_7; });
+  hercules-ci-agent = super.hercules-ci-agent.override { nix = pkgs.nixVersions.nix_2_7; };
+  hercules-ci-cnix-expr = super.hercules-ci-cnix-expr.override { nix = pkgs.nixVersions.nix_2_7; };
+  hercules-ci-cnix-store = super.hercules-ci-cnix-store.override { nix = pkgs.nixVersions.nix_2_7; };
 
   # Enable extra optimisations which increase build time, but also
   # later compiler performance, so we should do this for user's benefit.