diff --git a/build/build.py b/build/build.py
index <HASH>..<HASH> 100755
--- a/build/build.py
+++ b/build/build.py
@@ -49,7 +49,7 @@ import shakaBuildHelpers
 
 
 common_closure_opts = [
-    '--language_in', 'ECMASCRIPT5',
+    '--language_in', 'ECMASCRIPT6',
     '--language_out', 'ECMASCRIPT3',
 
     '--jscomp_error=*',
[ES6] Allow ES6 input in the Closure Compiler

Note that until we replace gjslint, the linter will still not accept
ES6 syntax.  So we cannot yet merge any commits which use ES6.

But this should allow us to start experimenting with ES6 locally by
bypassing the old linter.

Issue #<I>

Change-Id: Ic<I>f<I>a<I>f<I>b0a<I>c3e<I>cee6e<I>f