diff --git a/py-hftbacktest/hftbacktest/order.py b/py-hftbacktest/hftbacktest/order.py
index 416bb6e4..5b1194af 100644
--- a/py-hftbacktest/hftbacktest/order.py
+++ b/py-hftbacktest/hftbacktest/order.py
@@ -117,7 +117,7 @@ def tick_size(self) -> float64:
         """
         Returns the tick size.
         """
-        return self.arr[0].price_tick
+        return self.arr[0].tick_size
 
     @property
     def exch_timestamp(self) -> int64: