diff --git a/.eslintrc.json b/.eslintrc.json
index 84cef4f..1c6afb9 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -1,11 +1,9 @@
 {
   "parserOptions": {
-    "ecmaVersion": 5
+    "ecmaVersion": 6,
+    "sourceType": "module"
   },
   "extends": "eslint:recommended",
-  "env": {
-    "commonjs": true
-  },
   "rules": {
     "strict": [2, "global"],
     "block-scoped-var": 2,
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 43d2897..b6ebf3a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,6 +13,8 @@ jobs:
       - uses: actions/checkout@v2
 
       - uses: purescript-contrib/setup-purescript@main
+        with:
+          purescript: "unstable"
 
       - uses: actions/setup-node@v1
         with:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 19ca264..7e39446 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@ Notable changes to this project are documented in this file. The format is based
 ## [Unreleased]
 
 Breaking changes:
+- Migrate FFI to ES modules (#47 by @kl0tl and @JordanMartinez)
 
 New features:
 
diff --git a/bower.json b/bower.json
index 24fea18..5dcc7a0 100644
--- a/bower.json
+++ b/bower.json
@@ -17,12 +17,12 @@
     "package.json"
   ],
   "dependencies": {
-    "purescript-partial": "^3.0.0",
-    "purescript-prelude": "^5.0.0",
-    "purescript-tailrec": "^5.0.0",
-    "purescript-unsafe-coerce": "^5.0.0"
+    "purescript-partial": "master",
+    "purescript-prelude": "master",
+    "purescript-tailrec": "master",
+    "purescript-unsafe-coerce": "master"
   },
   "devDependencies": {
-    "purescript-console": "^5.0.0"
+    "purescript-console": "master"
   }
 }
diff --git a/package.json b/package.json
index fd4391e..a1d6811 100644
--- a/package.json
+++ b/package.json
@@ -7,8 +7,8 @@
   },
   "devDependencies": {
     "eslint": "^7.15.0",
-    "pulp": "^15.0.0",
-    "purescript-psa": "^0.8.0",
+    "pulp": "16.0.0-0",
+    "purescript-psa": "^0.8.2",
     "rimraf": "^3.0.2"
   }
 }
diff --git a/src/Control/Monad/ST/Internal.js b/src/Control/Monad/ST/Internal.js
index 7745a05..24d2ed8 100644
--- a/src/Control/Monad/ST/Internal.js
+++ b/src/Control/Monad/ST/Internal.js
@@ -1,6 +1,4 @@
-"use strict";
-
-exports.map_ = function (f) {
+export const map_ = function (f) {
   return function (a) {
     return function () {
       return f(a());
@@ -8,13 +6,13 @@ exports.map_ = function (f) {
   };
 };
 
-exports.pure_ = function (a) {
+export const pure_ = function (a) {
   return function () {
     return a;
   };
 };
 
-exports.bind_ = function (a) {
+export const bind_ = function (a) {
   return function (f) {
     return function () {
       return f(a())();
@@ -22,11 +20,11 @@ exports.bind_ = function (a) {
   };
 };
 
-exports.run = function (f) {
+export const run = function (f) {
   return f();
 };
 
-exports["while"] = function (f) {
+function whileST(f) {
   return function (a) {
     return function () {
       while (f()) {
@@ -34,9 +32,10 @@ exports["while"] = function (f) {
       }
     };
   };
-};
+}
+export { whileST as while };
 
-exports["for"] = function (lo) {
+function forST(lo) {
   return function (hi) {
     return function (f) {
       return function () {
@@ -46,9 +45,10 @@ exports["for"] = function (lo) {
       };
     };
   };
-};
+}
+export { forST as for };
 
-exports.foreach = function (as) {
+export const foreach = function (as) {
   return function (f) {
     return function () {
       for (var i = 0, l = as.length; i < l; i++) {
@@ -58,19 +58,20 @@ exports.foreach = function (as) {
   };
 };
 
-exports.new = function (val) {
+function newSTRef(val) {
   return function () {
     return { value: val };
   };
-};
+}
+export { newSTRef as new };
 
-exports.read = function (ref) {
+export const read = function (ref) {
   return function () {
     return ref.value;
   };
 };
 
-exports.modifyImpl = function (f) {
+export const modifyImpl = function (f) {
   return function (ref) {
     return function () {
       var t = f(ref.value);
@@ -80,7 +81,7 @@ exports.modifyImpl = function (f) {
   };
 };
 
-exports.write = function (a) {
+export const write = function (a) {
   return function (ref) {
     return function () {
       return ref.value = a; // eslint-disable-line no-return-assign