diff --git a/tools/releasetools/rangelib.py b/tools/releasetools/rangelib.py
index 36becf419..9d6e9fb17 100644
--- a/tools/releasetools/rangelib.py
+++ b/tools/releasetools/rangelib.py
@@ -52,9 +52,12 @@ class RangeSet(object):
   def __ne__(self, other):
     return self.data != other.data
 
-  def __nonzero__(self):
+  def __bool__(self):
     return bool(self.data)
 
+  # Python 2 uses __nonzero__, while Python 3 uses __bool__.
+  __nonzero__ = __bool__
+
   def __str__(self):
     if not self.data:
       return "empty"