diff --git a/bilingual.js b/bilingual.js
index 8475b3a..c5ee19b 100644
--- a/bilingual.js
+++ b/bilingual.js
@@ -1,3 +1,4 @@
+(function module() {
 // A list of all sections.
 let sectionList;
 
@@ -201,3 +202,4 @@ function readUserPreferences() {
 function writeUserPreferences() {
   localStorage.setItem(STORAGE_LANGUAGE_PREFERENCE_KEY, currentLanguage);
 }
+})()