diff --git a/README.md b/README.md
index 4b3da26..c403a50 100644
--- a/README.md
+++ b/README.md
@@ -34,6 +34,8 @@ Both keys and values of the `rewritePaths` object must end with a `/`. Paths are
 
 Output files are expected to have the `.js` extension.
 
+AVA searches your entire project for `*.js`, `*.cjs`, `*.mjs` and `*.ts` files (or other extensions you've configured). It will ignore such files found in the `rewritePaths` targets (e.g. `build/`). If you use more specific paths, for instance `build/main/`, you may need to change AVA's `files` configuration to ignore other directories.
+
 ## Add additional extensions
 
 You can configure AVA to recognize additional file extensions. To add (partial†) JSX support:
diff --git a/index.js b/index.js
index 5d0cd1e..c054114 100644
--- a/index.js
+++ b/index.js
@@ -2,10 +2,13 @@
 const path = require('path');
 
 const escapeStringRegexp = require('escape-string-regexp');
-const isPlainObject = require('is-plain-object');
 
 const pkg = require('./package.json');
 
+function isPlainObject(x) {
+	return x !== null && typeof x === 'object' && Reflect.getPrototypeOf(x) === Object.prototype;
+}
+
 function isValidExtensions(extensions) {
 	return Array.isArray(extensions) &&
 		extensions.length > 0 &&
diff --git a/package.json b/package.json
index 07b87ca..7e1ac53 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@ava/typescript",
-  "version": "1.1.0",
+  "version": "1.1.1",
   "description": "TypeScript provider for AVA",
   "engines": {
     "node": ">=10.18.0 <11 || >=12.14.0 <13 || >=13.5.0"
@@ -19,8 +19,7 @@
     "test": "xo && nyc ava"
   },
   "dependencies": {
-    "escape-string-regexp": "^2.0.0",
-    "is-plain-object": "^3.0.0"
+    "escape-string-regexp": "^2.0.0"
   },
   "devDependencies": {
     "ava": "^3.0.0",