diff --git a/pkgs/development/tools/parsing/tree-sitter/default.nix b/pkgs/development/tools/parsing/tree-sitter/default.nix
index e3435061563..37811943a6d 100644
--- a/pkgs/development/tools/parsing/tree-sitter/default.nix
+++ b/pkgs/development/tools/parsing/tree-sitter/default.nix
@@ -41,8 +41,10 @@ let
 
   builtGrammars = let
     change = name: grammar:
-      callPackage ./library.nix {
-        language = name; inherit version; source = fetchGrammar grammar;
+      callPackage ./library.nix {} {
+        language = name;
+        inherit version;
+        source = fetchGrammar grammar;
       };
   in
     # typescript doesn't have parser.c in the same place as others
@@ -60,10 +62,6 @@ in rustPlatform.buildRustPackage {
     # needed for the tests
     rm -rf test/fixtures/grammars
     ln -s ${grammars} test/fixtures/grammars
-
-    # These functions do not appear in the source code
-    sed -i /_ts_query_context/d lib/binding_web/exports.json
-    sed -i /___assert_fail/d lib/binding_web/exports.json
   '';
 
   # Compile web assembly with emscripten. The --debug flag prevents us from
diff --git a/pkgs/development/tools/parsing/tree-sitter/library.nix b/pkgs/development/tools/parsing/tree-sitter/library.nix
index 36245ff7d44..f78939b22ff 100644
--- a/pkgs/development/tools/parsing/tree-sitter/library.nix
+++ b/pkgs/development/tools/parsing/tree-sitter/library.nix
@@ -1,7 +1,15 @@
 { stdenv
-, language
 , tree-sitter
+}:
+
+# Build a parser grammar and put the resulting shared object in `$out/parser`
+
+{
+  # language name
+  language
+  # version of tree-sitter
 , version
+  # source for the language grammar
 , source
 }: