diff --git a/flake.nix b/flake.nix
index e6e67b910a042779ad3c37b28af52c73b212e206..91b59eabf20ac43c5f0ba1a132e77a1169939215 100644
--- a/flake.nix
+++ b/flake.nix
@@ -21,13 +21,6 @@
       # Get a nixpkgs customized for this system and including our overlay.
       pkgs = import nixpkgs {
         inherit system;
-        config = {
-          # XXX haskellPackages.language-ecmascript is marked as broken.  It
-          # is a dependency of an executable of tahoe-great-black-swamp (which
-          # we don't use, but gets dragged in because we depend on the
-          # tahoe-great-black-swamp library).
-          allowBroken = true;
-        };
       };
       hslib = hs-flake-utils.lib {
         inherit pkgs;
diff --git a/nix/haskell-packages.nix b/nix/haskell-packages.nix
index 91bdcbc9bd80e4c5ac243aa0a6de1006e9eea890..0411c50574ae51acb05dd80f11bd70435fdebcfe 100644
--- a/nix/haskell-packages.nix
+++ b/nix/haskell-packages.nix
@@ -1,4 +1,8 @@
 {haskellLib}: hfinal: hprev: {
   tahoe-chk = hfinal.callPackage ./tahoe-chk.nix {};
   tahoe-great-black-swamp = hfinal.callPackage ./tahoe-great-black-swamp.nix {};
+
+  # A broken dependency of a tahoe-great-black-swamp executable that we don't
+  # use.  Flip the broken bit so we can get a build.
+  language-ecmascript = haskellLib.unmarkBroken hprev.language-ecmascript;
 }