diff --git a/source/javascripts/app/_lang.js b/source/javascripts/app/_lang.js
index cc5ac8b6bd8..c1bd6b2a9b0 100644
--- a/source/javascripts/app/_lang.js
+++ b/source/javascripts/app/_lang.js
@@ -143,7 +143,7 @@ under the License.
     languages = l;
 
     var presetLanguage = getLanguageFromQueryString();
-    if (presetLanguage) {
+    if (presetLanguage  && languages.includes(presetLanguage)) {
       // the language is in the URL, so use that language!
       activateLanguage(presetLanguage);