--- a/js/xpconnect/loader/script_cache.py
+++ b/js/xpconnect/loader/script_cache.py
@@ -1,38 +1,41 @@
 #!/usr/bin/env python
 import io
 import os
 import struct
 import sys
 
-MAGIC = b'mozXDRcachev001\0'
+MAGIC = b'mozXDRcachev002\0'
 
 
 def usage():
     print("""Usage: script_cache.py <file.bin> ...
 
         Decodes and prints out the contents of a startup script cache file
         (e.g., startupCache/scriptCache.bin) in human-readable form.""")
 
     sys.exit(1)
 
 
 class ProcessTypes:
-    Default = 0
-    Web = 1
-    Extension = 2
-    Privileged = 3
+    Uninitialized = 0
+    Parent = 1
+    Web = 2
+    Extension = 3
+    Privileged = 4
 
     def __init__(self, val):
         self.val = val
 
     def __str__(self):
         res = []
-        if self.val & (1 << self.Default):
+        if self.val & (1 << self.Uninitialized):
+            raise Exception('Uninitialized process type')
+        if self.val & (1 << self.Parent):
             res.append('Parent')
         if self.val & (1 << self.Web):
             res.append('Web')
         if self.val & (1 << self.Extension):
             res.append('Extension')
         if self.val & (1 << self.Privileged):
             res.append('Privileged')
         return '|'.join(res)