diff --git a/lib/gui/app/models/store.js b/lib/gui/app/models/store.js
index 3c6c559e..cf53fc72 100644
--- a/lib/gui/app/models/store.js
+++ b/lib/gui/app/models/store.js
@@ -23,6 +23,7 @@ const uuidV4 = require('uuid/v4')
 const constraints = require('../../../shared/drive-constraints')
 const supportedFormats = require('../../../shared/supported-formats')
 const errors = require('../../../shared/errors')
+// eslint-disable-next-line node/no-missing-require
 const fileExtensions = require('../../../shared/file-extensions')
 const utils = require('../../../shared/utils')
 const settings = require('./settings')
diff --git a/lib/shared/file-extensions.js b/lib/shared/file-extensions.ts
similarity index 58%
rename from lib/shared/file-extensions.js
rename to lib/shared/file-extensions.ts
index b56f748e..af0ed8d9 100644
--- a/lib/shared/file-extensions.js
+++ b/lib/shared/file-extensions.ts
@@ -14,63 +14,50 @@
  * limitations under the License.
  */
 
-'use strict'
-
-const mime = require('mime-types')
-const _ = require('lodash')
+import * as _ from 'lodash';
+import { lookup } from 'mime-types';
 
 /**
  * @summary Get the extensions of a file
- * @function
- * @public
- *
- * @param {String} filePath - file path
- * @returns {String[]} extensions
  *
  * @example
  * const extensions = fileExtensions.getFileExtensions('path/to/foo.img.gz');
  * console.log(extensions);
  * > [ 'img', 'gz' ]
  */
-exports.getFileExtensions = _.memoize((filePath) => {
-  return _.chain(filePath)
-    .split('.')
-    .tail()
-    .map(_.toLower)
-    .value()
-})
+export function getFileExtensions(filePath: string): string[] {
+	return _.chain(filePath)
+		.split('.')
+		.tail()
+		.map(_.toLower)
+		.value();
+}
 
 /**
  * @summary Get the last file extension
- * @function
- * @public
- *
- * @param {String} filePath - file path
- * @returns {(String|Null)} last extension
  *
  * @example
  * const extension = fileExtensions.getLastFileExtension('path/to/foo.img.gz');
  * console.log(extension);
  * > 'gz'
  */
-exports.getLastFileExtension = (filePath) => {
-  return _.last(exports.getFileExtensions(filePath)) || null
+export function getLastFileExtension(filePath: string): string | null {
+	return _.last(getFileExtensions(filePath)) || null;
 }
 
 /**
  * @summary Get the penultimate file extension
- * @function
- * @public
- *
- * @param {String} filePath - file path
- * @returns {(String|Null)} penultimate extension
  *
  * @example
  * const extension = fileExtensions.getPenultimateFileExtension('path/to/foo.img.gz');
  * console.log(extension);
  * > 'img'
  */
-exports.getPenultimateFileExtension = (filePath) => {
-  const ext = _.last(_.initial(exports.getFileExtensions(filePath)))
-  return !_.isNil(ext) && mime.lookup(ext) ? ext : null
+export function getPenultimateFileExtension(filePath: string): string | null {
+	const extensions = getFileExtensions(filePath);
+	if (extensions.length >= 2) {
+		const ext = extensions[extensions.length - 2];
+		return lookup(ext) ? ext : null;
+	}
+	return null;
 }
diff --git a/lib/shared/supported-formats.js b/lib/shared/supported-formats.js
index 09592b51..e80747da 100644
--- a/lib/shared/supported-formats.js
+++ b/lib/shared/supported-formats.js
@@ -21,6 +21,7 @@ const _ = require('lodash')
 const mime = require('mime-types')
 const path = require('path')
 
+// eslint-disable-next-line node/no-missing-require
 const fileExtensions = require('./file-extensions')
 
 /**
diff --git a/npm-shrinkwrap.json b/npm-shrinkwrap.json
index 0c756ab7..7f4f4095 100644
--- a/npm-shrinkwrap.json
+++ b/npm-shrinkwrap.json
@@ -1186,6 +1186,12 @@
       "resolved": "https://registry.npmjs.org/@types/marked/-/marked-0.3.0.tgz",
       "integrity": "sha512-CSf9YWJdX1DkTNu9zcNtdCcn6hkRtB5ILjbhRId4ZOQqx30fXmdecuaXhugQL6eyrhuXtaHJ7PHI+Vm7k9ZJjg=="
     },
+    "@types/mime-types": {
+      "version": "2.1.0",
+      "resolved": "https://registry.npmjs.org/@types/mime-types/-/mime-types-2.1.0.tgz",
+      "integrity": "sha1-nKUs2jY/aZxpRmwqbM2q2RPqenM=",
+      "dev": true
+    },
     "@types/minimatch": {
       "version": "3.0.3",
       "resolved": "https://registry.npmjs.org/@types/minimatch/-/minimatch-3.0.3.tgz",
diff --git a/package.json b/package.json
index e0915bca..9692ae64 100644
--- a/package.json
+++ b/package.json
@@ -94,6 +94,7 @@
     "@babel/plugin-proposal-function-bind": "^7.2.0",
     "@babel/preset-env": "^7.6.0",
     "@babel/preset-react": "^7.0.0",
+    "@types/mime-types": "^2.1.0",
     "@types/node": "^12.12.24",
     "@types/react-dom": "^16.8.4",
     "babel-loader": "^8.0.4",
diff --git a/tests/shared/file-extensions.spec.js b/tests/shared/file-extensions.spec.js
index e5f241b6..3d43aca8 100644
--- a/tests/shared/file-extensions.spec.js
+++ b/tests/shared/file-extensions.spec.js
@@ -18,6 +18,7 @@
 
 const m = require('mochainon')
 const _ = require('lodash')
+// eslint-disable-next-line node/no-missing-require
 const fileExtensions = require('../../lib/shared/file-extensions')
 
 describe('Shared: fileExtensions', function () {