diff --git a/package.json b/package.json
index 602eb1e..65418cb 100644
--- a/package.json
+++ b/package.json
@@ -44,11 +44,11 @@
   "repository": "jdxcode/fancy-test",
   "scripts": {
     "build": "rm -rf lib && tsc",
-    "version": "markdown-toc -i README.md && git add README.md",
     "lint": "tsc -p test --noEmit && tslint -p test -t stylish",
     "posttest": "yarn run lint",
     "prepublishOnly": "yarn run build",
-    "test": "mocha --forbid-only \"test/**/*.test.ts\""
+    "test": "mocha --forbid-only \"test/**/*.test.ts\"",
+    "version": "markdown-toc -i README.md && git add README.md"
   },
   "types": "lib/index.d.ts"
 }
diff --git a/src/base.ts b/src/base.ts
index 5154112..d268714 100644
--- a/src/base.ts
+++ b/src/base.ts
@@ -140,6 +140,6 @@ export default base(context)
   .register('only', () => ({
     init: ctx => { ctx.test = it.only }
   }))
-  .register('retries', (count?: number) => ({
+  .register('retries', (count: number) => ({
     init: ctx => ctx.retries = count
   }))
diff --git a/src/catch.ts b/src/catch.ts
index 30a6c84..3659c0e 100644
--- a/src/catch.ts
+++ b/src/catch.ts
@@ -2,7 +2,7 @@ import * as _ from 'lodash'
 
 import {expect} from './chai'
 
-export default (arg?: RegExp | string | ((err: Error) => any), opts: {raiseIfNotThrown?: boolean} = {}) => ({
+export default (arg: RegExp | string | ((err: Error) => any), opts: {raiseIfNotThrown?: boolean} = {}) => ({
   run() {
     if (opts.raiseIfNotThrown !== false) {
       throw new Error('expected error to be thrown')
diff --git a/src/env.ts b/src/env.ts
index 0b1ecb2..569243b 100644
--- a/src/env.ts
+++ b/src/env.ts
@@ -2,7 +2,7 @@ import * as _ from 'lodash'
 
 import {EnvOptions} from './types'
 
-export default (env?: {[k: string]: string | null | undefined}, opts: EnvOptions = {}) => {
+export default (env: {[k: string]: string | null | undefined}, opts: EnvOptions = {}) => {
   const envs: (typeof process.env)[] = []
   return {
     run() {
diff --git a/src/nock.ts b/src/nock.ts
index 96e4147..88136c2 100644
--- a/src/nock.ts
+++ b/src/nock.ts
@@ -2,8 +2,7 @@ import Nock = require('nock')
 
 import {NockCallback, NockOptions} from './types'
 
-export function nock(host?: string, options?: NockCallback | NockOptions, cb?: NockCallback) {
-  if (host === undefined) throw new Error('host is undefined')
+export function nock(host: string, options: NockCallback | NockOptions, cb?: NockCallback) {
   if (typeof options === 'function') {
     cb = options
     options = {}
diff --git a/src/stdmock.ts b/src/stdmock.ts
index 49691e2..6c7afe5 100644
--- a/src/stdmock.ts
+++ b/src/stdmock.ts
@@ -17,7 +17,7 @@ const create = <T extends 'stdout' | 'stderr'>(std: T) => (opts: {print?: boolea
 
 export const stdout = create('stdout')
 export const stderr = create('stderr')
-export const stdin = (input?: string, delay = 0) => {
+export const stdin = (input: string, delay = 0) => {
   let stdin: any
   return {
     run: () => {
diff --git a/src/stub.ts b/src/stub.ts
index bd6373f..a6f7ffe 100644
--- a/src/stub.ts
+++ b/src/stub.ts
@@ -3,7 +3,7 @@ import * as _ from 'lodash'
 /**
  * mocks an object's property
  */
-export default function (object?: any, path?: string, value?: any) {
+export default function<T extends object, K extends keyof T> (object: T, path: K, value: () => T[K]) {
   if (object === undefined || path === undefined) throw new Error('should not be undefined')
   return {
     run(ctx: {stubs: any[]}) {
diff --git a/src/types.ts b/src/types.ts
index fefda19..bc8852f 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,9 +1,9 @@
-export type PluginBuilder<I, A1 = undefined, A2 = undefined, A3 = undefined, A4 = undefined> = (arg1?: A1, arg2?: A2, arg3?: A3, arg4?: A4) => Plugin<I>
+export type PluginBuilder<I, Args extends any[]> = (...args: Args) => Plugin<I>
 import Nock = require('nock')
 
 export interface Context {
   test: (typeof it | typeof it.skip)
-  plugins: {[k: string]: PluginBuilder<any, any, any, any, any>}
+  plugins: {[k: string]: PluginBuilder<any, any>}
   expectation?: string
   chain: Plugin<any>[]
   error?: Error & {code?: string}
@@ -20,10 +20,7 @@ export interface Plugin<I> {
 
 export interface PluginDef {
   output: object
-  a1: any
-  a2: any
-  a3: any
-  a4: any
+  args: any[]
 }
 
 export interface Plugins {[k: string]: PluginDef}
@@ -48,8 +45,8 @@ export type Base<I extends Context, T extends Plugins> = {
   add<K extends string, O>(key: K, cb: ((context: I) => Promise<O> | O) | Promise<O> | O): Base<I & {[P in K]: O}, T>
   do<O>(cb: (context: I & O) => any): Base<O & I, T>
   finally(cb: (context: I) => any): Base<I, T>
-  register<K extends string, O, A1, A2, A3, A4>(key: K, plugin: (arg1?: A1, arg2?: A2, arg3?: A3, arg4?: A4) => Plugin<O & I>): Base<I, T & {[P in K]: {output: O, a1: A1, a2: A2, a3: A3, a4: A4}}>
-} & {[P in keyof T]: (arg1?: T[P]['a1'], arg2?: T[P]['a2'], arg3?: T[P]['a3'], arg4?: T[P]['a4']) => Base<T[P]['output'] & I, T>}
+  register<K extends string, O, A extends any[]>(key: K, plugin: (...args: A) => Plugin<O & I>): Base<I, T & {[P in K]: {output: O, args: A}}>
+} & {[P in keyof T]: (...args: T[P]['args']) => Base<T[P]['output'] & I, T>}
 
 export interface EnvOptions {
   clear?: boolean
diff --git a/test/catch.test.ts b/test/catch.test.ts
index 4459371..ebbacc3 100644
--- a/test/catch.test.ts
+++ b/test/catch.test.ts
@@ -27,12 +27,12 @@ describe('catch', () => {
 
   fancy
     .do(() => { throw new Error('foobar') })
-    .catch()
+    .catch(undefined as any)
     .catch('no arg provided to catch')
     .end('errors if no args passed')
 
   fancy
-    .catch()
+    .catch(undefined as any)
     .catch('expected error to be thrown')
     .end('errors if no error thrown')