diff --git a/scripts/gulpfiles/build_tasks.js b/scripts/gulpfiles/build_tasks.js
index 0b102e12c..40adbbaab 100644
--- a/scripts/gulpfiles/build_tasks.js
+++ b/scripts/gulpfiles/build_tasks.js
@@ -116,8 +116,6 @@ function compile(compilerOptions, opt_verbose, opt_warnings_as_error,
   const options = {};
   options.compilation_level = 'SIMPLE_OPTIMIZATIONS';
   options.warning_level = opt_verbose ? 'VERBOSE' : 'DEFAULT';
-  // Use stable, regardless of what was passed in.
-  options.language_in = 'STABLE';
   options.language_out = 'ECMASCRIPT5_STRICT';
   options.rewrite_polyfills = false;
   options.hide_warnings_for = 'node_modules';