diff --git a/BUILD.gn b/BUILD.gn
index 485582643a..167ae82fbd 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -80,6 +80,11 @@ ts_sources = [
   "js/v8_source_maps.ts",
   "js/write_file.ts",
   "tsconfig.json",
+
+  # Listing package.json and yarn.lock as sources ensures the bundle is rebuilt
+  # when npm packages are added/removed or their contents changes.
+  "package.json",
+  "third_party/yarn.lock",
 ]
 
 rust_executable("deno") {
@@ -236,9 +241,7 @@ run_node("gen_declarations") {
 
 run_node("bundle") {
   out_dir = "$target_gen_dir/bundle/"
-  sources = ts_sources + [
-    "rollup.config.js",
-  ]
+  sources = ts_sources + [ "rollup.config.js" ]
   outputs = [
     out_dir + "main.js",
     out_dir + "main.js.map",