diff --git a/pkgs/development/haskell-modules/configuration-hackage2nix/main.yaml b/pkgs/development/haskell-modules/configuration-hackage2nix/main.yaml
index e4760fa54a2..da3a13d59dc 100644
--- a/pkgs/development/haskell-modules/configuration-hackage2nix/main.yaml
+++ b/pkgs/development/haskell-modules/configuration-hackage2nix/main.yaml
@@ -102,6 +102,7 @@ extra-packages:
   - haddock-api == 2.23.*               # required on GHC < 8.10.x
   - haddock-library ==1.7.*             # required by stylish-cabal-0.5.0.0
   - happy == 1.19.9                     # for purescript
+  - happy == 1.19.12                    # for ghcjs
   - hinotify == 0.3.9                   # for xmonad-0.26: https://github.com/kolmodin/hinotify/issues/29
   - hlint < 3.3                         # We don‘t have ghc-lib-parser 9.0.X yet.
   - immortal == 0.2.2.1                 # required by Hasura 1.3.1, 2020-08-20
diff --git a/pkgs/development/haskell-modules/hackage-packages.nix b/pkgs/development/haskell-modules/hackage-packages.nix
index 1c77e1f9723..0a18b6fd5ff 100644
--- a/pkgs/development/haskell-modules/hackage-packages.nix
+++ b/pkgs/development/haskell-modules/hackage-packages.nix
@@ -116710,6 +116710,22 @@ self: {
        hydraPlatforms = lib.platforms.none;
      }) {};
 
+  "happy_1_19_12" = callPackage
+    ({ mkDerivation, array, base, containers, mtl, process }:
+     mkDerivation {
+       pname = "happy";
+       version = "1.19.12";
+       sha256 = "03xlmq6qmdx4zvzw8bp33kd9g7yvcq5cz4wg50xilw812kj276pv";
+       isLibrary = false;
+       isExecutable = true;
+       enableSeparateDataOutput = true;
+       executableHaskellDepends = [ array base containers mtl ];
+       testHaskellDepends = [ base process ];
+       description = "Happy is a parser generator for Haskell";
+       license = lib.licenses.bsd2;
+       hydraPlatforms = lib.platforms.none;
+     }) {};
+
   "happy" = callPackage
     ({ mkDerivation, array, base, containers, mtl, process }:
      mkDerivation {