diff --git a/example/cjs/index.cjs b/example/cjs/index.cjs
index 760cae9..c6f6024 100644
--- a/example/cjs/index.cjs
+++ b/example/cjs/index.cjs
@@ -1,10 +1,10 @@
-const Rand = require('../../dist/index.cjs').default;
-const PRNG = require('../../dist/index.cjs');
+const Rand = require('../../dist/cjs/index.js').default;
+const { PRNG } = require('../../dist/cjs/index.js');
 
 let rand = new Rand('1234', PRNG.mulberry32);
 const result1 = Array.from({ length: 10 }, () => rand.next());
 
-rand = new Rand('1234');
+rand = new Rand('1234', PRNG.mulberry32);
 const result2 = Array.from({ length: 10 }, () => rand.next());
 
 console.log('RESULT1:', result1);
diff --git a/example/es/index.js b/example/es/index.js
index 911cce4..d800028 100644
--- a/example/es/index.js
+++ b/example/es/index.js
@@ -1,9 +1,9 @@
-import Rand, { PRNG } from '../../dist/index.js';
+import Rand, { PRNG } from '../../dist/es/index.js';
 
 let rand = new Rand('1234', PRNG.mulberry32);
 const result1 = Array.from({ length: 10 }, () => rand.next());
 
-rand = new Rand('1234');
+rand = new Rand('1234', PRNG.mulberry32);
 const result2 = Array.from({ length: 10 }, () => rand.next());
 
 console.log('RESULT1:', result1);
diff --git a/package.json b/package.json
index 4d9fb4c..1409390 100644
--- a/package.json
+++ b/package.json
@@ -5,12 +5,12 @@
   "exports": {
     ".": {
       "import": {
-        "types": "./dist/index.d.ts",
-        "default": "./dist/index.js"
+        "types": "./dist/es/index.d.ts",
+        "default": "./dist/es/index.js"
       },
       "require": {
-        "types": "./dist/index.d.ts",
-        "default": "./dist/index.cjs"
+        "types": "./dist/cjs/index.d.ts",
+        "default": "./dist/cjs/index.js"
       }
     }
   },
@@ -18,7 +18,6 @@
   "files": [
     "dist"
   ],
-  "types": "dist/index.d.ts",
   "scripts": {
     "test": "cross-env NODE_ENV=test ./node_modules/.bin/jest",
     "lint": "npx eslint .",
diff --git a/rollup.config.ts b/rollup.config.ts
index d5bc4f7..d46738e 100644
--- a/rollup.config.ts
+++ b/rollup.config.ts
@@ -1,3 +1,5 @@
+import fs from 'fs';
+
 import typescript from '@rollup/plugin-typescript';
 import terser from '@rollup/plugin-terser';
 import clean from '@rollup-extras/plugin-clean';
@@ -10,14 +12,14 @@ export default defineConfig({
     output: [
         {
             dir: './dist',
-            entryFileNames: 'index.cjs',
+            entryFileNames: 'cjs/index.js',
             format: 'cjs',
             sourcemap: local,
             exports: 'named',
         },
         {
             dir: './dist',
-            entryFileNames: 'index.js',
+            entryFileNames: 'es/index.js',
             format: 'es',
             sourcemap: local,
         },
@@ -25,5 +27,49 @@ export default defineConfig({
     watch: {
         include: 'src/**',
     },
-    plugins: [clean('dist'), typescript({ sourceMap: local }), terser()],
+    plugins: [
+        clean('dist'),
+        typescript({ sourceMap: local }),
+        terser(),
+        (() => ({
+            name: 'collectCjsTypeDeclaration',
+            writeBundle: {
+                sequential: true,
+                order: 'post',
+                handler: ({ format }) => {
+                    if (format !== 'cjs') {
+                        return;
+                    }
+
+                    fs.readdir('./dist/es', { recursive: true }, (err, list) => {
+                        for (const item of list) {
+                            if (item.toString().endsWith('.js')) {
+                                continue;
+                            }
+
+                            if (fs.lstatSync(`./dist/es/${item.toString()}`).isDirectory()) {
+                                if (!fs.existsSync(`./dist/cjs/${item.toString()}`)) {
+                                    fs.mkdirSync(`./dist/cjs/${item.toString()}`, { recursive: true });
+                                }
+
+                                continue;
+                            }
+
+                            fs.copyFile(`./dist/es/${item}`, `./dist/cjs/${item}`, (err) => {
+                                if (err) {
+                                    console.error(err);
+                                }
+
+                                fs.writeFile('./dist/cjs/package.json', '{\n\t"type": "commonjs"\n}', (err) => {
+                                    if (err) {
+                                        console.error(err);
+                                    }
+                                });
+                            });
+                        }
+                    });
+                },
+            },
+        }))(),
+    ],
 });
diff --git a/src/Rand.ts b/src/Rand.ts
index a09d037..c804a8e 100644
--- a/src/Rand.ts
+++ b/src/Rand.ts
@@ -28,7 +28,7 @@ class Rand {
      * The string that will be used for generating a suitable hash for any of
      * the provided PRNG algorithms.
      *
-     * @var {string}
+     * @var {string|undefined}
      */
     private str?: string;
 
@@ -49,8 +49,8 @@ class Rand {
     /**
      * Create a new rand instance.
      *
-     * @param {string} str
-     * @param {PRNG} prng
+     * @param {string|undefined} str
+     * @param {PRNG|undefined} prng
      */
     public constructor(str?: string, prng: PRNG = PRNG.sfc32) {
         this.str = str;
diff --git a/tsconfig.base.json b/tsconfig.base.json
index c0b0d3e..f155a96 100644
--- a/tsconfig.base.json
+++ b/tsconfig.base.json
@@ -7,12 +7,11 @@
     "resolveJsonModule": true,
     "verbatimModuleSyntax": true,
     "useDefineForClassFields": true,
-    "esModuleInterop": true,
     "forceConsistentCasingInFileNames": true,
     "skipLibCheck": true,
     "strict": true,
     "declaration": true,
-    "declarationDir": "./dist",
+    "declarationDir": "./dist/es",
     "rootDir": "./src",
     "outDir": "./dist"
   },
diff --git a/tsconfig.json b/tsconfig.json
index 82e63f2..50dfc0f 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,3 +1,6 @@
 {
-  "extends": "./tsconfig.base"
+  "extends": "./tsconfig.base",
+  "compilerOptions": {
+    "esModuleInterop": false
+  }
 }
diff --git a/tsconfig.test.json b/tsconfig.test.json
index 1cc5e6e..e28740f 100644
--- a/tsconfig.test.json
+++ b/tsconfig.test.json
@@ -1,6 +1,7 @@
 {
   "extends": "./tsconfig.base",
   "compilerOptions": {
+    "esModuleInterop": true,
     "verbatimModuleSyntax": false
   },
   "include": ["__tests__/**/*"]