diff --git a/once/once-tests.ts b/once/once-tests.ts
new file mode 100644
index 0000000000..05f60f0400
--- /dev/null
+++ b/once/once-tests.ts
@@ -0,0 +1,13 @@
+/// <reference path="once.d.ts" />
+
+import once from "once";
+
+once(() => 3);
+once(() => 3)();
+let s = once(() => ({foo: 1}))();
+s.foo;
+
+once.proto();
+
+once(() => 3).called && true;
+once(() => ({foo: 1})).value.foo;
diff --git a/once/once.d.ts b/once/once.d.ts
new file mode 100644
index 0000000000..a0aa60e798
--- /dev/null
+++ b/once/once.d.ts
@@ -0,0 +1,23 @@
+// Type definitions for once v1.3.3
+// Project: https://github.com/isaacs/once
+// Definitions by: Denis Sokolov <https://github.com/denis-sokolov>
+// Definitions: https://github.com/borisyankov/DefinitelyTyped
+
+interface SimpleFunction<Result> {
+  (...args: any[]): Result;
+}
+
+interface OnceFunction<Result> extends SimpleFunction<Result> {
+  called: boolean;
+  value: Result;
+}
+
+interface Once {
+  <Result>(f: SimpleFunction<Result>): OnceFunction<Result>;
+  proto: Function;
+}
+
+declare module "once" {
+  var once: Once;
+  export default once;
+}