diff --git a/WaveshareUARTFingerprintSensor/FingerprintSensor.cs b/WaveshareUARTFingerprintSensor/FingerprintSensor.cs
index a4a9026..c4004ba 100644
--- a/WaveshareUARTFingerprintSensor/FingerprintSensor.cs
+++ b/WaveshareUARTFingerprintSensor/FingerprintSensor.cs
@@ -79,7 +79,7 @@ namespace WaveshareUARTFingerprintSensor
         {
             byte checksum = 0;
 
-            for (int i = 1; i < length + 1; i++)
+            for (int i = 1; i < length; i++)
             {
                 checksum ^= data[i];
             }