diff --git a/lib/hd/mnemonic.js b/lib/hd/mnemonic.js
index 0922d766..2b5dc397 100644
--- a/lib/hd/mnemonic.js
+++ b/lib/hd/mnemonic.js
@@ -356,7 +356,7 @@ Mnemonic.getLanguage = function getLanguage(word) {
   for (i = 0; i < Mnemonic.languages.length; i++) {
     lang = Mnemonic.languages[i];
     wordlist = Mnemonic.getWordlist(lang);
-    if (wordlist.indexOf(word) !== -1)
+    if (utils.binarySearch(wordlist, word, utils.strcmp) !== -1)
       return lang;
   }