diff --git a/src/text-mate-language-mode.js b/src/text-mate-language-mode.js
index a8907b0fb..123e39f58 100644
--- a/src/text-mate-language-mode.js
+++ b/src/text-mate-language-mode.js
@@ -716,7 +716,7 @@ class TextMateLanguageMode {
   }
 }
 
-TextMateLanguageMode.chunkSize = 50
+TextMateLanguageMode.prototype.chunkSize = 50
 
 function selectorMatchesAnyScope (selector, scopes) {
   const targetClasses = selector.replace(/^\./, '').split('.')