diff --git a/package.json b/package.json
index 47a3bb9e..8181607f 100644
--- a/package.json
+++ b/package.json
@@ -35,6 +35,7 @@
     "markdown-doctest": "^0.9.1",
     "nyc": "^11.4.1",
     "rollup": "^0.55.1",
+    "rollup-plugin-commonjs": "^8.3.0",
     "rollup-plugin-multi-entry": "^2.0.2",
     "rollup-plugin-node-resolve": "^3.0.2",
     "semantic-release": "^12.2.5",
diff --git a/rollup.config.js b/rollup.config.js
index 2192f7c4..43f54e6f 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -1,12 +1,12 @@
 import pkg from './package.json';
 import resolve from 'rollup-plugin-node-resolve';
-
+import commonjs from 'rollup-plugin-commonjs';
 export default {
   output: {
     file: pkg.main,
     format: 'cjs'
   },
-  plugins: [resolve()],
+  plugins: [resolve(), commonjs()],
   external: [
     'os',
     'util',
diff --git a/tests/rollup.config.js b/tests/rollup.config.js
index 4d472e35..273962a7 100644
--- a/tests/rollup.config.js
+++ b/tests/rollup.config.js
@@ -1,5 +1,6 @@
 import multiEntry from 'rollup-plugin-multi-entry';
 import resolve from 'rollup-plugin-node-resolve';
+import commonjs from 'rollup-plugin-commonjs';
 
 export default {
   input: 'tests/**/*-test.js',
@@ -14,7 +15,7 @@ export default {
     'expression-expander',
     'pratt-parser'
   ],
-  plugins: [multiEntry(), resolve()],
+  plugins: [multiEntry(), resolve(), commonjs()],
 
   output: {
     file: 'build/bundle-test.js',