diff --git a/src/expression.js b/src/expression.js
index d1d0b7457a..de02eb585b 100755
--- a/src/expression.js
+++ b/src/expression.js
@@ -250,7 +250,7 @@ pp.parseExprAtom = function(refShorthandDefaultPos) {
     return this.finishNode(node, type)
 
   case tt._yield:
-    if (this.inGenerator) unexpected()
+    if (this.inGenerator) this.unexpected()
 
   case tt._do:
     if (this.options.features["es7.doExpressions"]) {