diff --git a/src/params.rs b/src/params.rs
index 2acc7e1..f733b61 100644
--- a/src/params.rs
+++ b/src/params.rs
@@ -4,7 +4,7 @@ use crate::param::SendParam;
 
 pub trait SendParams {
     fn len(&self, long: bool) -> usize {
-        self.param_len(long) + if long { 2 } else { 1 }
+        self.param_len(long) + 1
     }
 
     fn param_len(&self, long: bool) -> usize;
diff --git a/src/transport/spi.rs b/src/transport/spi.rs
index 41db49b..b3bdd57 100644
--- a/src/transport/spi.rs
+++ b/src/transport/spi.rs
@@ -81,7 +81,7 @@ where
             // Pad to 4 byte boundary
             let mut total_len = send_params.len(long_send) + 3;
             while 0 != total_len % 4 {
-                Self::send_byte(spi, 0)?;
+                Self::send_byte(spi, 0xff)?;
                 total_len += 1;
             }