diff --git a/lib/output.js b/lib/output.js
index 6c1d61a3..f60b474c 100644
--- a/lib/output.js
+++ b/lib/output.js
@@ -576,7 +576,7 @@ function OutputStream(options) {
         indentation     : function() { return indentation },
         current_width   : function() { return current_col - indentation },
         should_break    : function() { return options.width && this.current_width() >= options.width },
-        has_parens      : function() { return OUTPUT.slice(-1) == "(" },
+        has_parens      : function() { return OUTPUT[OUTPUT.length - 1] == "(" },
         newline         : newline,
         print           : print,
         space           : space,