diff --git a/scripts/copy-res.ts b/scripts/copy-res.ts
index 5954bc05ae..cf3a0477a0 100755
--- a/scripts/copy-res.ts
+++ b/scripts/copy-res.ts
@@ -165,7 +165,7 @@ function watchLanguage(lang: string, dest: string, langFileMap: Record<string, s
     // XXX: Use a debounce because for some reason if we read the language
     // file immediately after the FS event is received, the file contents
     // appears empty. Possibly https://github.com/nodejs/node/issues/6112
-    let makeLangDebouncer: number;
+    let makeLangDebouncer: ReturnType<typeof setTimeout>;
     const makeLang = (): void => {
         if (makeLangDebouncer) {
             clearTimeout(makeLangDebouncer);
diff --git a/src/@types/cpx.d.ts b/src/@types/cpx.d.ts
index f1980d932a..d9c4d632e3 100644
--- a/src/@types/cpx.d.ts
+++ b/src/@types/cpx.d.ts
@@ -15,12 +15,16 @@ limitations under the License.
 */
 
 import "cpx";
-import type EventEmitter from "events";
 
 declare module "cpx" {
-    export class Cpx extends EventEmitter {
+    export class Cpx {
         public constructor(source: string, outDir: string, options?: object);
 
+        public on(eventName: "copy", fn: (event: { srcPath: string; dstPath: string }) => void): void;
+        public on(eventName: "remove", fn: (event: { path: string }) => void): void;
+        public on(eventName: "watch-ready", fn: () => void): void;
+        public on(eventName: "watch-error", fn: (error: Error) => void): void;
+
         /**
          * Copy all files that matches `this.source` pattern to `this.outDir`.
          *
diff --git a/tsconfig.json b/tsconfig.json
index 5762df78d4..c707ebaa54 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -26,5 +26,8 @@
         "./test/**/*.ts",
         "./test/**/*.tsx",
         "./scripts/*.ts"
-    ]
+    ],
+    "ts-node": {
+        "files": true
+    }
 }