diff --git a/lib/6to5/runtime.js b/lib/6to5/runtime.js
index ee77d65c60..5fa34fc7c5 100644
--- a/lib/6to5/runtime.js
+++ b/lib/6to5/runtime.js
@@ -8,10 +8,7 @@ module.exports = function (namespace) {
   var body = [];
   var container = t.functionExpression(null, [], t.blockStatement(body));
 
-  var tree = {
-    type: "Program",
-    body: [t.expressionStatement(t.callExpression(container, []))]
-  };
+  var tree = t.program([t.expressionStatement(t.callExpression(container, []))]);
 
   body.push(t.variableDeclaration("var", [
     t.variableDeclarator(t.identifier("self"), t.conditionalExpression(