diff --git a/BUILD.bazel b/BUILD.bazel
index 61afe5e..e291b64 100644
--- a/BUILD.bazel
+++ b/BUILD.bazel
@@ -1,21 +1,19 @@
 load("@ai_formation_hazel//:hazel.bzl", "hazel_library")
 load("@io_tweag_rules_haskell//haskell:haskell.bzl", "haskell_library", "haskell_test")
+load("//third_party/haskell/alex:build_defs.bzl", "alex_lexer")
+load("//third_party/haskell/happy:build_defs.bzl", "happy_parser")
 load("//tools/project:build_defs.bzl", "project")
 
 project()
 
-genrule(
+alex_lexer(
     name = "Lexer",
-    srcs = ["src/Tokstyle/Cimple/Lexer.x"],
-    outs = ["src/Tokstyle/Cimple/Lexer.hs"],
-    cmd = "alex -o $@ $<",
+    src = "src/Tokstyle/Cimple/Lexer.x",
 )
 
-genrule(
+happy_parser(
     name = "Parser",
-    srcs = ["src/Tokstyle/Cimple/Parser.y"],
-    outs = ["src/Tokstyle/Cimple/Parser.hs"],
-    cmd = "happy -agc -o $@ $<",
+    src = "src/Tokstyle/Cimple/Parser.y",
 )
 
 haskell_library(