diff --git a/lib/rewriter.js b/lib/rewriter.js
index 84eaf6de..1f84a221 100644
--- a/lib/rewriter.js
+++ b/lib/rewriter.js
@@ -288,7 +288,7 @@
       if (unclosed.length) {
         open = unclosed[0];
         line = open_line[open] + 1;
-        throw new Error("unclosed " + (open) + " on line " + (line));
+        throw new Error("unclosed " + open + " on line " + line);
       }
     };
     // We'd like to support syntax like this:
diff --git a/src/rewriter.coffee b/src/rewriter.coffee
index 62cd9fc3..a542f72d 100644
--- a/src/rewriter.coffee
+++ b/src/rewriter.coffee
@@ -189,7 +189,7 @@ exports.Rewriter: class Rewriter
     if unclosed.length
       open: unclosed[0]
       line: open_line[open] + 1
-      throw new Error("unclosed ${open} on line ${line}")
+      throw new Error "unclosed $open on line $line"
 
   # We'd like to support syntax like this:
   #