diff --git a/pkgs/development/tools/parsing/tree-sitter/default.nix b/pkgs/development/tools/parsing/tree-sitter/default.nix
index c077913b1eb1..e3d74600c955 100644
--- a/pkgs/development/tools/parsing/tree-sitter/default.nix
+++ b/pkgs/development/tools/parsing/tree-sitter/default.nix
@@ -20,6 +20,7 @@
 , enableShared ? !stdenv.hostPlatform.isStatic
 , enableStatic ? stdenv.hostPlatform.isStatic
 , webUISupport ? false
+, extraGrammars ? {}
 }:
 
 # TODO: move to carnix or https://github.com/kolloch/crate2nix
@@ -51,19 +52,18 @@ let
     runCommand "grammars" { } (''
       mkdir $out
     '' + (lib.concatStrings (lib.mapAttrsToList
-      (name: grammar: "ln -s ${fetchGrammar grammar} $out/${name}\n")
+      (name: grammar: "ln -s ${if grammar ? src then grammar.src else fetchGrammar grammar} $out/${name}\n")
       (import ./grammars { inherit lib; }))));
-
   builtGrammars =
     let
       change = name: grammar:
         callPackage ./grammar.nix { } {
           language = if grammar ? language then grammar.language else name;
           inherit version;
-          source = fetchGrammar grammar;
+          source = if grammar ? src then grammar.src else fetchGrammar grammar;
           location = if grammar ? location then grammar.location else null;
         };
-      grammars' = (import ./grammars { inherit lib; });
+      grammars' = import ./grammars { inherit lib; } // extraGrammars;
       grammars = grammars' //
         { tree-sitter-ocaml = grammars'.tree-sitter-ocaml // { location = "ocaml"; }; } //
         { tree-sitter-ocaml-interface = grammars'.tree-sitter-ocaml // { location = "interface"; }; } //
@@ -71,7 +71,7 @@ let
         { tree-sitter-typescript = grammars'.tree-sitter-typescript // { location = "typescript"; }; } //
         { tree-sitter-tsx = grammars'.tree-sitter-typescript // { location = "tsx"; }; };
     in
-    lib.mapAttrs change grammars;
+      lib.mapAttrs change (grammars);
 
   # Usage:
   # pkgs.tree-sitter.withPlugins (p: [ p.tree-sitter-c p.tree-sitter-java ... ])
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 40ea0a4f8bbe..31d25dc9197a 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -15932,7 +15932,7 @@ with pkgs;
 
   travis = callPackage ../development/tools/misc/travis { };
 
-  tree-sitter = callPackage ../development/tools/parsing/tree-sitter {
+  tree-sitter = makeOverridable (callPackage ../development/tools/parsing/tree-sitter) {
     inherit (darwin.apple_sdk.frameworks) Security;
   };