diff --git a/types/onetime/index.d.ts b/types/onetime/index.d.ts
index c7406307bc..f1c6b56ad0 100644
--- a/types/onetime/index.d.ts
+++ b/types/onetime/index.d.ts
@@ -1,36 +1,45 @@
-// Type definitions for onetime 2.0
+// Type definitions for onetime 3.0
 // Project: https://github.com/sindresorhus/onetime#readme
 // Definitions by: BendingBender <https://github.com/BendingBender>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+// TypeScript Version: 3.0
 
 export = oneTime;
 
-declare function oneTime<R>(fn: () => R, options?: oneTime.Options): () => R;
-declare function oneTime<T1, R>(fn: (t1: T1) => R, options?: oneTime.Options): (t1: T1) => R;
-declare function oneTime<T1, T2, R>(fn: (t1: T1, t2: T2) => R, options?: oneTime.Options): (t1: T1, t2: T2) => R;
-declare function oneTime<T1, T2, T3, R>(fn: (t1: T1, t2: T2, t3: T3) => R, options?: oneTime.Options): (t1: T1, t2: T2, t3: T3) => R;
-declare function oneTime<T1, T2, T3, T4, R>(
-    fn: (t1: T1, t2: T2, t3: T3, t4: T4) => R, options?: oneTime.Options): (t1: T1, t2: T2, t3: T3, t4: T4) => R;
-declare function oneTime<T1, T2, T3, T4, T5, R>(
-    fn: (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5) => R, options?: oneTime.Options): (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5) => R;
-declare function oneTime<T1, T2, T3, T4, T5, T6, R>(
-    fn: (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6) => R, options?: oneTime.Options): (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6) => R;
-declare function oneTime<T1, T2, T3, T4, T5, T6, T7, R>(
-    fn: (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7) => R,
-    options?: oneTime.Options): (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7) => R;
-declare function oneTime<T1, T2, T3, T4, T5, T6, T7, T8, R>(
-    fn: (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, t8: T8) => R,
-    options?: oneTime.Options): (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, t8: T8) => R;
-declare function oneTime<T1, T2, T3, T4, T5, T6, T7, T8, T9, R>(
-    fn: (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, t8: T8, t9: T9) => R,
-    options?: oneTime.Options): (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, t8: T8, t9: T9) => R;
-declare function oneTime<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, R>(
-    fn: (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, t8: T8, t9: T9, t10: T10) => R,
-    options?: oneTime.Options): (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, t8: T8, t9: T9, t10: T10) => R;
-declare function oneTime<R>(fn: (...args: any[]) => R, options?: oneTime.Options): (...args: any[]) => R;
+/**
+ * Ensure a function is only called once. When called multiple times it will return the return value from the first call.
+ *
+ * @param fn Function that should only be called once.
+ * @returns A function that only calls `fn` once.
+ */
+declare function oneTime<T extends any[], R>(
+    fn: (...args: T) => R,
+    options?: oneTime.Options
+): (...args: T) => R;
 
 declare namespace oneTime {
+    /**
+     * Get the number of times `fn` has been called.
+     *
+     * @param fn Function to get call count from.
+     * @returns A number representing how many times `fn` has been called.
+     *
+     * @example
+     * const foo = onetime(() => {});
+     * foo();
+     * foo();
+     * foo();
+     *
+     * console.log(onetime.callCount(foo));
+     * //=> 3
+     */
+    function callCount(fn: (...args: any[]) => any): number | undefined;
+
     interface Options {
+        /**
+         * Throw an error when called more than once.
+         * @default false
+         */
         throw?: boolean;
     }
 }
diff --git a/types/onetime/onetime-tests.ts b/types/onetime/onetime-tests.ts
index 840edb6cc2..4678eb45db 100644
--- a/types/onetime/onetime-tests.ts
+++ b/types/onetime/onetime-tests.ts
@@ -3,29 +3,10 @@ import onetime = require('onetime');
 const foo = onetime(() => 5);
 foo(); // $ExpectType number
 
-const foo2 = onetime(() => true, {throw: true});
+const foo2 = onetime(() => true, { throw: true });
 foo2(); // $ExpectType boolean
 
 onetime((t1: boolean) => 5)(true); // $ExpectType number
 onetime((t1: boolean, t2: string) => 5)(true, ''); // $ExpectType number
-onetime((t1: boolean, t2: string, t3: number) => 5)(true, '', 5); // $ExpectType number
-onetime((t1: boolean, t2: string, t3: number, t4: undefined) => 5)(true, '', 5, undefined); // $ExpectType number
-onetime((t1: boolean, t2: string, t3: number, t4: undefined, t5: string) => 5)(true, '', 5, undefined, ''); // $ExpectType number
-onetime((t1: boolean, t2: string, t3: number, t4: undefined, t5: string, t6: number) => 5)(true, '', 5, undefined, '', 6); // $ExpectType number
-onetime((t1: boolean, t2: string, t3: number, t4: undefined, t5: string, t6: number, t7: boolean) => 5)(true, '', 5, undefined, '', 6, false); // $ExpectType number
 
-const t8 = onetime(
-    (t1: boolean, t2: string, t3: number, t4: undefined, t5: string, t6: number, t7: boolean, t8: string) => 5);
-t8(true, '', 5, undefined, '', 6, false, ''); // $ExpectType number
-
-const t9 = onetime(
-    (t1: boolean, t2: string, t3: number, t4: undefined, t5: string, t6: number, t7: boolean, t8: string, t9: number) => 5);
-t9(true, '', 5, undefined, '', 6, false, '', 1); // $ExpectType number
-
-const t10 = onetime(
-    (t1: boolean, t2: string, t3: number, t4: undefined, t5: string, t6: number, t7: boolean, t8: string, t9: number, t10: boolean) => 5);
-t10(true, '', 5, undefined, '', 6, false, '', 1, true); // $ExpectType number
-
-const t11 = onetime(
-    (t1: boolean, t2: string, t3: number, t4: undefined, t5: string, t6: number, t7: boolean, t8: string, t9: number, t10: boolean, t11: string) => 5);
-t11(true, '', 5, undefined, '', 6, false, '', 1, true, 5); // $ExpectType number
+onetime.callCount((t1: boolean, t2: string) => 5); // $ExpectType number | undefined
diff --git a/types/onetime/tsconfig.json b/types/onetime/tsconfig.json
index 84d3da86b8..39df78e5bc 100644
--- a/types/onetime/tsconfig.json
+++ b/types/onetime/tsconfig.json
@@ -20,4 +20,4 @@
         "index.d.ts",
         "onetime-tests.ts"
     ]
-}
\ No newline at end of file
+}
diff --git a/types/onetime/v2/index.d.ts b/types/onetime/v2/index.d.ts
new file mode 100644
index 0000000000..c7406307bc
--- /dev/null
+++ b/types/onetime/v2/index.d.ts
@@ -0,0 +1,36 @@
+// Type definitions for onetime 2.0
+// Project: https://github.com/sindresorhus/onetime#readme
+// Definitions by: BendingBender <https://github.com/BendingBender>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+export = oneTime;
+
+declare function oneTime<R>(fn: () => R, options?: oneTime.Options): () => R;
+declare function oneTime<T1, R>(fn: (t1: T1) => R, options?: oneTime.Options): (t1: T1) => R;
+declare function oneTime<T1, T2, R>(fn: (t1: T1, t2: T2) => R, options?: oneTime.Options): (t1: T1, t2: T2) => R;
+declare function oneTime<T1, T2, T3, R>(fn: (t1: T1, t2: T2, t3: T3) => R, options?: oneTime.Options): (t1: T1, t2: T2, t3: T3) => R;
+declare function oneTime<T1, T2, T3, T4, R>(
+    fn: (t1: T1, t2: T2, t3: T3, t4: T4) => R, options?: oneTime.Options): (t1: T1, t2: T2, t3: T3, t4: T4) => R;
+declare function oneTime<T1, T2, T3, T4, T5, R>(
+    fn: (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5) => R, options?: oneTime.Options): (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5) => R;
+declare function oneTime<T1, T2, T3, T4, T5, T6, R>(
+    fn: (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6) => R, options?: oneTime.Options): (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6) => R;
+declare function oneTime<T1, T2, T3, T4, T5, T6, T7, R>(
+    fn: (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7) => R,
+    options?: oneTime.Options): (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7) => R;
+declare function oneTime<T1, T2, T3, T4, T5, T6, T7, T8, R>(
+    fn: (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, t8: T8) => R,
+    options?: oneTime.Options): (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, t8: T8) => R;
+declare function oneTime<T1, T2, T3, T4, T5, T6, T7, T8, T9, R>(
+    fn: (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, t8: T8, t9: T9) => R,
+    options?: oneTime.Options): (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, t8: T8, t9: T9) => R;
+declare function oneTime<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, R>(
+    fn: (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, t8: T8, t9: T9, t10: T10) => R,
+    options?: oneTime.Options): (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, t8: T8, t9: T9, t10: T10) => R;
+declare function oneTime<R>(fn: (...args: any[]) => R, options?: oneTime.Options): (...args: any[]) => R;
+
+declare namespace oneTime {
+    interface Options {
+        throw?: boolean;
+    }
+}
diff --git a/types/onetime/v2/onetime-tests.ts b/types/onetime/v2/onetime-tests.ts
new file mode 100644
index 0000000000..840edb6cc2
--- /dev/null
+++ b/types/onetime/v2/onetime-tests.ts
@@ -0,0 +1,31 @@
+import onetime = require('onetime');
+
+const foo = onetime(() => 5);
+foo(); // $ExpectType number
+
+const foo2 = onetime(() => true, {throw: true});
+foo2(); // $ExpectType boolean
+
+onetime((t1: boolean) => 5)(true); // $ExpectType number
+onetime((t1: boolean, t2: string) => 5)(true, ''); // $ExpectType number
+onetime((t1: boolean, t2: string, t3: number) => 5)(true, '', 5); // $ExpectType number
+onetime((t1: boolean, t2: string, t3: number, t4: undefined) => 5)(true, '', 5, undefined); // $ExpectType number
+onetime((t1: boolean, t2: string, t3: number, t4: undefined, t5: string) => 5)(true, '', 5, undefined, ''); // $ExpectType number
+onetime((t1: boolean, t2: string, t3: number, t4: undefined, t5: string, t6: number) => 5)(true, '', 5, undefined, '', 6); // $ExpectType number
+onetime((t1: boolean, t2: string, t3: number, t4: undefined, t5: string, t6: number, t7: boolean) => 5)(true, '', 5, undefined, '', 6, false); // $ExpectType number
+
+const t8 = onetime(
+    (t1: boolean, t2: string, t3: number, t4: undefined, t5: string, t6: number, t7: boolean, t8: string) => 5);
+t8(true, '', 5, undefined, '', 6, false, ''); // $ExpectType number
+
+const t9 = onetime(
+    (t1: boolean, t2: string, t3: number, t4: undefined, t5: string, t6: number, t7: boolean, t8: string, t9: number) => 5);
+t9(true, '', 5, undefined, '', 6, false, '', 1); // $ExpectType number
+
+const t10 = onetime(
+    (t1: boolean, t2: string, t3: number, t4: undefined, t5: string, t6: number, t7: boolean, t8: string, t9: number, t10: boolean) => 5);
+t10(true, '', 5, undefined, '', 6, false, '', 1, true); // $ExpectType number
+
+const t11 = onetime(
+    (t1: boolean, t2: string, t3: number, t4: undefined, t5: string, t6: number, t7: boolean, t8: string, t9: number, t10: boolean, t11: string) => 5);
+t11(true, '', 5, undefined, '', 6, false, '', 1, true, 5); // $ExpectType number
diff --git a/types/onetime/v2/tsconfig.json b/types/onetime/v2/tsconfig.json
new file mode 100644
index 0000000000..bda103d103
--- /dev/null
+++ b/types/onetime/v2/tsconfig.json
@@ -0,0 +1,28 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "lib": [
+            "es6"
+        ],
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictNullChecks": true,
+        "strictFunctionTypes": true,
+        "baseUrl": "../../",
+        "typeRoots": [
+            "../../"
+        ],
+        "paths": {
+            "onetime": [
+                "onetime/v2"
+            ]
+        },
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true
+    },
+    "files": [
+        "index.d.ts",
+        "onetime-tests.ts"
+    ]
+}
diff --git a/types/onetime/v2/tslint.json b/types/onetime/v2/tslint.json
new file mode 100644
index 0000000000..3db14f85ea
--- /dev/null
+++ b/types/onetime/v2/tslint.json
@@ -0,0 +1 @@
+{ "extends": "dtslint/dt.json" }