diff --git a/src/as/com/threerings/util/StringBuilder.as b/src/as/com/threerings/util/StringBuilder.as
index 820cbe4d0..85a36534f 100644
--- a/src/as/com/threerings/util/StringBuilder.as
+++ b/src/as/com/threerings/util/StringBuilder.as
@@ -14,7 +14,7 @@ public class StringBuilder
     public function append (... args) :StringBuilder
     {
         while (args.length > 0) {
-            _array.push(args.shift());
+            _array.push(String(args.shift()));
         }
         return this;
     }