diff --git a/package.json b/package.json
index 93764c987a..f0453c3db7 100644
--- a/package.json
+++ b/package.json
@@ -47,7 +47,6 @@
     "ui/tournament",
     "ui/tournamentSchedule",
     "ui/tree",
-    "ui/@types/defer-promise",
     "ui/@types/lichess"
   ]
 }
diff --git a/ui/@types/defer-promise/index.d.ts b/ui/@types/defer-promise/index.d.ts
deleted file mode 100644
index d3fe72b750..0000000000
--- a/ui/@types/defer-promise/index.d.ts
+++ /dev/null
@@ -1,11 +0,0 @@
-interface Deferred<T> {
-  promise: Promise<T>;
-  resolve(value: T | PromiseLike<T>): void;
-  resolve(this: Deferred<void>): void;
-  reject(reason?: any): void;
-}
-
-declare module 'defer-promise' {
-  function defer<T>(): Deferred<T>;
-  export = defer;
-}
diff --git a/ui/@types/defer-promise/package.json b/ui/@types/defer-promise/package.json
deleted file mode 100644
index 37b8533410..0000000000
--- a/ui/@types/defer-promise/package.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "name": "@types/defer-promise",
-  "version": "1.0.0",
-  "author": "Thibault Duplessis",
-  "license": "AGPL-3.0"
-}
diff --git a/ui/ceval/src/stockfishProtocol.ts b/ui/ceval/src/stockfishProtocol.ts
index 4227fa34e6..66346ddbc7 100644
--- a/ui/ceval/src/stockfishProtocol.ts
+++ b/ui/ceval/src/stockfishProtocol.ts
@@ -13,7 +13,7 @@ export default class Protocol {
   private work: Work | null = null;
   private curEval: Tree.ClientEval | null = null;
   private expectedPvs = 1;
-  private stopped: Deferred<void> | null;
+  private stopped: DeferPromise.Deferred<void> | null;
   private opts: WorkerOpts;
 
   constructor(send: (cmd: string) => void, opts: WorkerOpts) {
diff --git a/yarn.lock b/yarn.lock
index e56b84cc40..3118b513ac 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -19,6 +19,10 @@
     normalize-path "^2.0.1"
     through2 "^2.0.3"
 
+"@types/defer-promise@1.0.0":
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/@types/defer-promise/-/defer-promise-1.0.0.tgz#9c5054b7ef63fd0f0497d17b0ea1a849f9c6323b"
+
 "@types/jquery@*":
   version "3.2.16"
   resolved "https://registry.yarnpkg.com/@types/jquery/-/jquery-3.2.16.tgz#04419c404a3194350e7d3f339a90e72c88db3111"