diff --git a/lib/mwUtil.js b/lib/mwUtil.js
index a43704b8d..69aad65ae 100644
--- a/lib/mwUtil.js
+++ b/lib/mwUtil.js
@@ -86,23 +86,24 @@ mwUtil.canConvertLangVariant = (hyper, req, pageLanguage) => {
  * a page in a requested language on a particular wiki.
  * @param {HyperSwitch} hyper
  * @param {Object} req
- * @param {string} pageLanguage the language of the requested page.
- * @param {string} acceptLanguage the language variant accepted by the client.
+ * @param {string} pageLang the language of the requested page.
+ * @param {string} acceptLang the language variant accepted by the client.
  * @return {Promise<boolean>}
  */
-mwUtil.shouldConvertLangVariant = (hyper, req, pageLanguage, acceptLanguage) => {
-    if (!acceptLanguage) {
+mwUtil.shouldConvertLangVariant = (hyper, req, pageLang, acceptLang) => {
+    if (!acceptLang) {
         return P.resolve(false);
     }
     return mwUtil.getSiteInfo(hyper, req)
     .then((siteInfo) => {
+        const pageLangWithFallback = pageLang ? pageLang.toLowerCase() : siteInfo.general.lang;
         // First, whether specialized variants exist for the page lang on a wiki
-        const pageLangVariants = siteInfo.languagevariants[pageLanguage.toLowerCase()];
+        const pageLangVariants = siteInfo.languagevariants[pageLangWithFallback];
         if (!pageLangVariants) {
             return false;
         }
         // Second, if the requested language variant exist for page language
-        return pageLangVariants.indexOf(acceptLanguage.toLowerCase()) !== -1;
+        return pageLangVariants.indexOf(acceptLang.toLowerCase()) !== -1;
     });
 };