diff --git a/selfdrive/car/rivian/riviancan.py b/selfdrive/car/rivian/riviancan.py
index 3ecdaa08ca9fd1..1598f8dfe953bb 100644
--- a/selfdrive/car/rivian/riviancan.py
+++ b/selfdrive/car/rivian/riviancan.py
@@ -1,6 +1,6 @@
 def checksum(data, prefix, poly):
   crc = 0
-  data = [prefix] + data
+  data = bytes(prefix) + data
   for byte in data:
     crc ^= byte
     for _ in range(8):