diff --git a/lib/output.js b/lib/output.js
index e8fd1cfe..ba6785ae 100644
--- a/lib/output.js
+++ b/lib/output.js
@@ -171,15 +171,15 @@ function OutputStream(options) {
     }
 
     var quote_string = [
-        function(str, quote, dq, sq) {
-            return dq > sq ? quote_single(str) : quote_double(str);
-        },
+        null,
         quote_single,
         quote_double,
         function(str, quote) {
             return quote == "'" ? quote_single(str) : quote_double(str);
         },
-    ][options.quote_style];
+    ][options.quote_style] || function(str, quote, dq, sq) {
+        return dq > sq ? quote_single(str) : quote_double(str);
+    };
 
     function make_string(str, quote) {
         var dq = 0, sq = 0;