diff --git a/psopacket/src/lib.rs b/psopacket/src/lib.rs
index f9ed7a4..fc050d2 100644
--- a/psopacket/src/lib.rs
+++ b/psopacket/src/lib.rs
@@ -177,7 +177,7 @@ fn generate_psopacket_impl(pkt_cmd: u16, name: syn::Ident, attrs: &Vec<AttrType>
                     buf.push(0);
                 }
 
-                let pkt_len = (buf.len() + 8) as u16;
+                let pkt_len = (buf.len() + if #include_flag { 8 } else { 4 }) as u16;
                 let mut prebuf: Vec<u8> = Vec::new();
 
                 prebuf.extend_from_slice(&u16::to_le_bytes(pkt_len));