diff --git a/source/i18n.js b/source/i18n.js
index ce175dc27..412e17b6d 100644
--- a/source/i18n.js
+++ b/source/i18n.js
@@ -2,16 +2,12 @@ import i18next from 'i18next'
 import queryString from 'query-string'
 import { initReactI18next } from 'react-i18next'
 import enTranslations from './locales/en.yaml'
-import { getIframeOption, parseDataAttributes } from './utils'
-
-let getFromSessionStorage = where =>
-	typeof sessionStorage !== 'undefined' ? sessionStorage[where] : null
-
-let setToSessionStorage = (where, what) =>
-	typeof sessionStorage !== 'undefined' &&
-	do {
-		sessionStorage[where] = what
-	}
+import {
+	getFromSessionStorage,
+	getIframeOption,
+	parseDataAttributes,
+	setToSessionStorage
+} from './utils'
 
 let lang =
 	getIframeOption('lang') ||
diff --git a/source/sites/mon-entreprise.fr/App.js b/source/sites/mon-entreprise.fr/App.js
index dc0df1d71..ada37929c 100644
--- a/source/sites/mon-entreprise.fr/App.js
+++ b/source/sites/mon-entreprise.fr/App.js
@@ -21,7 +21,7 @@ import {
 	retrievePersistedSimulation
 } from '../../storage/persistSimulation'
 import ReactPiwik from '../../Tracker'
-import { inIframe } from '../../utils'
+import { inIframe, setToSessionStorage } from '../../utils'
 import './App.css'
 import Footer from './layout/Footer/Footer'
 import Header from './layout/Header/Header'
@@ -60,9 +60,7 @@ const middlewares = [
 
 class InFranceRoute extends Component {
 	componentDidMount() {
-		if (typeof sessionStorage !== 'undefined') {
-			sessionStorage['lang'] = this.props.language
-		}
+		setToSessionStorage('lang', this.props.language)
 	}
 	render() {
 		const paths = constructLocalizedSitePath(this.props.language)
diff --git a/source/utils.js b/source/utils.js
index 2752334b6..7c6502008 100644
--- a/source/utils.js
+++ b/source/utils.js
@@ -66,7 +66,7 @@ export function inIframe() {
 	}
 }
 
-export function softCatch<ArgType: any, ReturnType: any>(
+export function softCatch<ArgType: mixed, ReturnType: mixed>(
 	fn: ArgType => ReturnType
 ): ArgType => ReturnType | null {
 	return function(...args) {
@@ -102,3 +102,13 @@ export const constructSitePaths = (
 		sitePaths
 	)
 })
+
+export const getFromSessionStorage = softCatch<string, any>(where => {
+	typeof sessionStorage !== 'undefined' ? sessionStorage[where] : null
+})
+
+export const setToSessionStorage = softCatch<string, void>((where, what) => {
+	if (typeof sessionStorage !== 'undefined') {
+		sessionStorage[where] = what
+	}
+})