diff --git a/frontend/escheck.js b/frontend/escheck.js
deleted file mode 100644
index 4b27c465..00000000
--- a/frontend/escheck.js
+++ /dev/null
@@ -1,28 +0,0 @@
-const spawn = require('child_process').spawn;
-const path = require('path');
-
-module.exports = function({ mode = 'es5', glob } = {}) {
-  return new Promise((resolve, reject) => {
-    if (!glob) {
-      reject(new Error('no glob provided'));
-    }
-    const check = spawn('./node_modules/.bin/es-check', [mode, glob], {
-      cwd: path.resolve(__dirname, './'),
-    });
-
-    const buffer = [];
-
-    check.stdout.on('data', data => {
-      buffer.push(data.toString('utf-8'));
-    });
-
-    check.stderr.on('data', data => {
-      buffer.push(data.toString('utf-8'));
-    });
-
-    check.on('close', code => {
-      if (code === 0) resolve();
-      reject(new Error(`es-check exited with code ${code}\n\n${buffer.join('\n')}`));
-    });
-  });
-};
diff --git a/frontend/package-lock.json b/frontend/package-lock.json
index 126761de..f8f65834 100644
--- a/frontend/package-lock.json
+++ b/frontend/package-lock.json
@@ -2978,9 +2978,9 @@
       "dev": true
     },
     "bluebird": {
-      "version": "3.5.3",
-      "resolved": "https://registry.npmjs.org/bluebird/-/bluebird-3.5.3.tgz",
-      "integrity": "sha512-/qKPUQlaW1OyR51WeCPBvRnAlnZFUJkCSG5HzGnuIqhgyJtF+T94lFnn33eiazjRm2LAHVy2guNnaq48X9SJuw==",
+      "version": "3.7.2",
+      "resolved": "https://registry.npmjs.org/bluebird/-/bluebird-3.7.2.tgz",
+      "integrity": "sha512-XpNj6GDQzdfW+r2Wnn7xiSAd7TM3jzkxGXBGTtWKuSXv1xUV+azxAm8jdWZN06QTQk+2N2XB9jRDkvbmQmcRtg==",
       "dev": true
     },
     "bn.js": {
@@ -3378,18 +3378,16 @@
       "dev": true
     },
     "caporal": {
-      "version": "1.1.0",
-      "resolved": "https://registry.npmjs.org/caporal/-/caporal-1.1.0.tgz",
-      "integrity": "sha512-R5qo2QGoqBM6RvzHonGhUuEJSeqEa4lD1r+cPUEY2+YsXhpQVTS2TvScfIbi6ydFdhzFCNeNUB1v0YrRBvsbdg==",
+      "version": "1.3.0",
+      "resolved": "https://registry.npmjs.org/caporal/-/caporal-1.3.0.tgz",
+      "integrity": "sha512-4bj21UXbEu5cF+1gVjhwwRqMhY3lR7CUTlBr6YX3uzftL4l/sbu8EoHfOLZWHr+HeiosW9fTWkQCS2UZMAk5lw==",
       "dev": true,
       "requires": {
         "bluebird": "^3.4.7",
         "cli-table3": "^0.5.0",
-        "colorette": "1.0.1",
+        "colorette": "^1.0.1",
         "fast-levenshtein": "^2.0.6",
-        "lodash.camelcase": "^4.3.0",
-        "lodash.kebabcase": "^4.1.1",
-        "lodash.merge": "^4.6.0",
+        "lodash": "^4.17.14",
         "micromist": "1.1.0",
         "prettyjson": "^1.2.1",
         "tabtab": "^2.2.2",
@@ -3755,9 +3753,9 @@
       "dev": true
     },
     "colorette": {
-      "version": "1.0.1",
-      "resolved": "https://registry.npmjs.org/colorette/-/colorette-1.0.1.tgz",
-      "integrity": "sha512-40MnlppkzHhFjRhtXunbpqKUT+eJn0gyVGi8aQlNSG8T2CCy31NdD7yktcS0aizH1VP2OhhQCyGMeTp0a/fvaw==",
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/colorette/-/colorette-1.1.0.tgz",
+      "integrity": "sha512-6S062WDQUXi6hOfkO/sBPVwE5ASXY4G2+b4atvhJfSsuUUhIaUKlkjLe9692Ipyt5/a+IPF5aVTu3V5gvXq5cg==",
       "dev": true
     },
     "colors": {
@@ -4902,20 +4900,20 @@
       }
     },
     "es-check": {
-      "version": "5.0.0",
-      "resolved": "https://registry.npmjs.org/es-check/-/es-check-5.0.0.tgz",
-      "integrity": "sha512-30n+EZt5KjazXEvyYr2DXJCOJJWfdT1unRp5+Szlcja6uGAB3Sh3QPjRsxd2xgN9SFj4S5P8pdBISwGcDdS45Q==",
+      "version": "5.1.0",
+      "resolved": "https://registry.npmjs.org/es-check/-/es-check-5.1.0.tgz",
+      "integrity": "sha512-QlRhlUmEpdnleBFYWRFROm8u9cNPOWdE1iXQPWiQXnwmlJZ0hSxWpLOXwpFLyRrwnTmt5xqYM/5OR8Ao0MYa8w==",
       "dev": true,
       "requires": {
-        "acorn": "6.0.4",
-        "caporal": "1.1.0",
+        "acorn": "6.1.1",
+        "caporal": "1.3.0",
         "glob": "^7.1.2"
       },
       "dependencies": {
         "acorn": {
-          "version": "6.0.4",
-          "resolved": "https://registry.npmjs.org/acorn/-/acorn-6.0.4.tgz",
-          "integrity": "sha512-VY4i5EKSKkofY2I+6QLTbTTN/UvEQPCo6eiwzzSaSWfpaDhOmStMCMod6wmuPciNq+XS0faCglFu2lHZpdHUtg==",
+          "version": "6.1.1",
+          "resolved": "https://registry.npmjs.org/acorn/-/acorn-6.1.1.tgz",
+          "integrity": "sha512-jPTiwtOxaHNaAPg/dmrJ/beuzLRnXtB0kQPQ8JpotKJgTB6rX6c8mlf315941pyjBSaPg8NHXS9fhP4u17DpGA==",
           "dev": true
         }
       }
@@ -10143,12 +10141,6 @@
       "integrity": "sha1-yaR3SYYHUB2OhJTSg7h8OSgc72I=",
       "dev": true
     },
-    "lodash.kebabcase": {
-      "version": "4.1.1",
-      "resolved": "https://registry.npmjs.org/lodash.kebabcase/-/lodash.kebabcase-4.1.1.tgz",
-      "integrity": "sha1-hImxyw0p/4gZXM7KRI/21swpXDY=",
-      "dev": true
-    },
     "lodash.keys": {
       "version": "3.1.2",
       "resolved": "https://registry.npmjs.org/lodash.keys/-/lodash.keys-3.1.2.tgz",
@@ -10166,12 +10158,6 @@
       "integrity": "sha1-vMbEmkKihA7Zl/Mj6tpezRguC/4=",
       "dev": true
     },
-    "lodash.merge": {
-      "version": "4.6.2",
-      "resolved": "https://registry.npmjs.org/lodash.merge/-/lodash.merge-4.6.2.tgz",
-      "integrity": "sha512-0KpjqXRVvrYyCsX1swR/XTK0va6VQkQM6MNo7PqW77ByjAhoARA8EfrP1N4+KlKj8YS0ZUCtRT/YUuhyYDujIQ==",
-      "dev": true
-    },
     "lodash.pad": {
       "version": "4.5.1",
       "resolved": "https://registry.npmjs.org/lodash.pad/-/lodash.pad-4.5.1.tgz",
diff --git a/frontend/package.json b/frontend/package.json
index 453c474a..23239dba 100644
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -2,7 +2,7 @@
   "name": "remark-ui",
   "version": "0.1.0",
   "scripts": {
-    "build": "webpack --mode production && node postbuild.js",
+    "build": "webpack --mode production && es-check es5 './public/*.js'",
     "start": "webpack-dev-server --mode development",
     "check": "tsc -p tsconfig.json --noEmit --skipLibCheck",
     "lint": "eslint --max-warnings=0 --ext=.ts,.tsx,.js,.jsx .",
@@ -53,7 +53,7 @@
     "document-register-element": "^1.14.3",
     "enzyme": "^3.10.0",
     "enzyme-adapter-preact-pure": "^2.1.0",
-    "es-check": "^5.0.0",
+    "es-check": "^5.1.0",
     "eslint": "^6.6.0",
     "eslint-config-prettier": "^6.5.0",
     "eslint-plugin-jsx-a11y": "^6.2.3",
diff --git a/frontend/postbuild.js b/frontend/postbuild.js
deleted file mode 100644
index 4fc15d31..00000000
--- a/frontend/postbuild.js
+++ /dev/null
@@ -1,15 +0,0 @@
-/* eslint-disable no-console */
-
-const escheck = require('./escheck');
-
-async function main() {
-  try {
-    console.log('checking es5 compatibility...');
-    escheck({ glob: './public/*.js' });
-  } catch (e) {
-    console.error(e);
-    process.exit(1);
-  }
-}
-
-main();