diff --git a/test/input/issue-520/input.js b/test/input/issue-520/input.js
index 62428a52..3ea89900 100644
--- a/test/input/issue-520/input.js
+++ b/test/input/issue-520/input.js
@@ -1,3 +1,4 @@
 var Foo = function Foo(){console.log(1+2);}; new Foo();
 
+//# sourceMappingURL=data:application/json;charset=utf-8;base64,I/am/not/a/sourceMappingURL/but/a/comment
 //# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJmaWxlIjpudWxsLCJzb3VyY2VzIjpbInN0ZGluIl0sInNvdXJjZXNDb250ZW50IjpbImNsYXNzIEZvbyB7IGNvbnN0cnVjdG9yKCl7Y29uc29sZS5sb2coMSsyKTt9IH0gbmV3IEZvbygpO1xuIl0sIm5hbWVzIjpbXSwibWFwcGluZ3MiOiJBQUFBLElBQU0sR0FBRyxHQUFDLEFBQUUsWUFBVyxFQUFFLENBQUMsT0FBTyxDQUFDLEdBQUcsQ0FBQyxDQUFDLENBQUMsQ0FBQyxDQUFDLENBQUMsQ0FBQyxDQUFBLEFBQUUsQ0FBQyxJQUFJLEdBQUcsRUFBRSxDQUFDOyJ9