diff --git a/acorn.js b/acorn.js
index f5e9d835e3..d6e7acb738 100644
--- a/acorn.js
+++ b/acorn.js
@@ -164,7 +164,7 @@
         comments.push(comment);
       };
     }
-    if (opts.strictMode) {
+    if (options.strictMode) {
       strict = true;
     }
     isKeyword = options.ecmaVersion >= 6 ? isEcma6Keyword : isEcma5AndLessKeyword;