diff --git a/tools/releasetools/rangelib.py b/tools/releasetools/rangelib.py
index 87380a5..8af61c3 100644
--- a/tools/releasetools/rangelib.py
+++ b/tools/releasetools/rangelib.py
@@ -25,6 +25,7 @@
 
   def __init__(self, data=None):
     self.monotonic = False
+    self._extra = {}
     if isinstance(data, str):
       self._parse_internal(data)
     elif data:
@@ -56,6 +57,10 @@
   def __repr__(self):
     return '<RangeSet("' + self.to_string() + '")>'
 
+  @property
+  def extra(self):
+    return self._extra
+
   @classmethod
   def parse(cls, text):
     """Parse a text string consisting of a space-separated list of