diff --git a/hptp/src/msg.rs b/hptp/src/msg.rs
index 1946b09..cf33e3b 100644
--- a/hptp/src/msg.rs
+++ b/hptp/src/msg.rs
@@ -21,9 +21,10 @@ pub enum DownMsg {
 pub struct DesError;
 
 pub trait SerDes: Sized {
-    // For both methods: `buf.len()` must be >= `MAX_SERIALIZED_SIZE`
-
+    // `buf.len()` must be <= `MAX_TOTAL_PACKET_SIZE`
     fn des(buf: &[u8]) -> Result<Self, DesError>;
+
+    // `buf.len()` must be >= `MAX_TOTAL_PACKET_SIZE`
     fn ser_to(&self, buf: &mut [u8]) -> usize;
 }