diff --git a/mbv/prog.py b/mbv/prog.py
index 31f8d89..c8508f0 100644
--- a/mbv/prog.py
+++ b/mbv/prog.py
@@ -8,7 +8,7 @@ import time
 offset = 0x80000000
 tty = '/dev/ttyUSB1'
 baud = 115200
-chunksize = 128
+chunksize = 1024
 
 
 def write(s, offset, dat):