diff --git a/lib/6to5/transformation/transformers/es6/tail-call.js b/lib/6to5/transformation/transformers/es6/tail-call.js
index 3f8888f84e..37581f7a96 100644
--- a/lib/6to5/transformation/transformers/es6/tail-call.js
+++ b/lib/6to5/transformation/transformers/es6/tail-call.js
@@ -132,6 +132,8 @@ TailCallTransformer.prototype.run = function () {
 };
 
 TailCallTransformer.prototype.subTransform = function (node) {
+  if (!node) return;
+
   var handler = this["subTransform" + node.type];
   if (handler) return handler.call(this, node);
 };
@@ -324,8 +326,10 @@ var secondPass = {
 var thirdPass = {
   enter: function (node, parent, scope, state) {
     if (!t.isExpressionStatement(node)) return;
+
     var expr = node.expression;
     if (!t.isAssignmentExpression(expr)) return;
+
     if (!state.needsThis && expr.left === state.getThisId()) {
       this.remove();
     } else if (!state.needsArguments && expr.left === state.getArgumentsId() && t.isArrayExpression(expr.right)) {