diff --git a/lib/index.js b/lib/index.js
index a4eea19..47cce0c 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -129,13 +129,13 @@ function restoreReadFileContext(binding) {
 /**
  * Swap out the fs bindings for a mock file system.
  * @param {Object} config Mock file system configuration.
- * @param {Object} options Any filesystem options.
+ * @param {Object} [options={}] Any filesystem options.
  * @param {boolean} options.createCwd Create a directory for `process.cwd()`
  *     (defaults to `true`).
  * @param {boolean} options.createTmp Create a directory for `os.tmpdir()`
  *     (defaults to `true`).
  */
-exports = module.exports = function mock(config, options) {
+exports = module.exports = function mock(config, options = {}) {
   const system = FileSystem.create(config, options);
   const binding = new Binding(system);