diff --git a/lib/bq27441/bq27441/device.py b/lib/bq27441/bq27441/device.py
index ab50cac4..4772d958 100644
--- a/lib/bq27441/bq27441/device.py
+++ b/lib/bq27441/bq27441/device.py
@@ -530,7 +530,7 @@ def compute_block_checksum(self):
         for i in range(32):
             csum += data[i]
 
-        csum = 255 - csum
+        csum = (255 - (csum & 0xFF)) & 0xFF
         return csum
 
     # Use the block_data_checksum command to write a checksum value