diff -r 001389026dbf -r ed0c92c81ea4 emul/src/main/java/java/lang/String.java
--- a/emul/src/main/java/java/lang/String.java	Tue Dec 04 11:21:10 2012 +0100
+++ b/emul/src/main/java/java/lang/String.java	Wed Dec 05 09:28:31 2012 +0100
@@ -1767,7 +1767,7 @@
      *          or {@code -1} if there is no such occurrence.
      */
     @JavaScriptBody(args = { "self", "str", "fromIndex" }, body =
-        "return self.toString().indexOf(str.toString(), fromIndex) >= 0;"
+        "return self.toString().indexOf(str.toString(), fromIndex);"
     )
     public int indexOf(String str, int fromIndex) {
         return indexOf(toCharArray(), offset(), length(), str.toCharArray(), str.offset(), str.length(), fromIndex);