diff --git a/goodix.py b/goodix.py
index b98009d..aca9418 100644
--- a/goodix.py
+++ b/goodix.py
@@ -334,7 +334,7 @@ def write_sensor_register(self, address: int | list[int],
 
             message = b""
             message += b"\x01"
-            for i in length:
+            for i in range(length):
                 if len(value[i]) != 2:
                     raise ValueError("Invalid value")