bug in Safari javascript RegExp?

This code splits the string into 2 pieces in Firefox and IE,
but just 1 piece in Safari. It seems like a bug in RegExp.
The "i" flag is supposed to mean the expression is
case-insensitive.

var r = new RegExp("x", "i");
var s = "helloXbye";
var parts = s.split(r);
alert("split into " + parts.length + " parts");


Windoze Windows XP