diff --git a/cake/libs/string.php b/cake/libs/string.php
index a85db0065..eae2d24ac 100644
--- a/cake/libs/string.php
+++ b/cake/libs/string.php
@@ -136,13 +136,13 @@ class String extends Object {
 			$pid = getmypid();
 		}
 
-		if (!$pid) {
+		if (!$pid || $pid > 65535) {
 			$pid = mt_rand(0, 0xfff) | 0x4000;
 		}
 
 		list($timeMid, $timeLow) = explode(' ', microtime());
 		$uuid = sprintf("%08x-%04x-%04x-%02x%02x-%04x%08x", (int)$timeLow, (int)substr($timeMid, 2) & 0xffff,
-					mt_rand(0, 0xfff) | 0x4000, mt_rand(0, 0x3f) | 0x80, mt_rand(0, 0xff), substr($pid, 0, 5), $node);
+					mt_rand(0, 0xfff) | 0x4000, mt_rand(0, 0x3f) | 0x80, mt_rand(0, 0xff), $pid, $node);
 
 		return $uuid;
 	}