diff --git a/pkgs/development/haskell-modules/configuration-nix.nix b/pkgs/development/haskell-modules/configuration-nix.nix
index fb08481a39de0..a8cc966de02ee 100644
--- a/pkgs/development/haskell-modules/configuration-nix.nix
+++ b/pkgs/development/haskell-modules/configuration-nix.nix
@@ -938,8 +938,14 @@ self: super: builtins.intersectAttrs super {
 
   cachix = generateOptparseApplicativeCompletion "cachix" (super.cachix.override { nix = pkgs.nix_2_4; });
 
-  hercules-ci-agent = appendConfigureFlag "-fnix-2_4" (super.hercules-ci-agent.override { nix = pkgs.nix_2_4; });
-  hercules-ci-cnix-expr = appendConfigureFlag "-fnix-2_4" (super.hercules-ci-cnix-expr.override { nix = pkgs.nix_2_4; });
+  hercules-ci-agent = appendConfigureFlag "-fnix-2_4" (super.hercules-ci-agent.override {
+    nix = pkgs.nix_2_4;
+    bdw-gc = null; # must be propagated from Nix instead.
+  });
+  hercules-ci-cnix-expr = appendConfigureFlag "-fnix-2_4" (super.hercules-ci-cnix-expr.override {
+    nix = pkgs.nix_2_4;
+    bdw-gc = null; # must be propagated from Nix instead.
+  });
   hercules-ci-cnix-store = appendConfigureFlag "-fnix-2_4" (super.hercules-ci-cnix-store.override { nix = pkgs.nix_2_4; });
 
   # Enable extra optimisations which increase build time, but also