diff --git a/lib/rex/book/limit_volume_tracker.rb b/lib/rex/book/limit_volume_tracker.rb
index e4e8cfe..8cf42d5 100644
--- a/lib/rex/book/limit_volume_tracker.rb
+++ b/lib/rex/book/limit_volume_tracker.rb
@@ -1,7 +1,7 @@
 module Rex
   module Book
     class LimitVolumeTracker
-      LimitVolumeChange = Struct.new(:side, :price, :new_volume)
+      LimitVolumeChange = Struct.new(:side, :price, :quantity)
 
       attr_reader :volumes