diff --git a/src/protocol/codec.rs b/src/protocol/codec.rs
index 0054372c9..0ce55cc99 100644
--- a/src/protocol/codec.rs
+++ b/src/protocol/codec.rs
@@ -200,7 +200,7 @@ impl<R: AsyncRead + Unpin> Decoder<R> {
                     .context("decoding packet after decompressing")?;
                 ensure!(
                     decompressed.is_empty(),
-                    "packet contents were not read completely"
+                    format!("packet contents were not read completely, {} remaining bytes", decompressed.len())
                 );
                 packet
             } else {
diff --git a/src/protocol/packets/c2s.rs b/src/protocol/packets/c2s.rs
index 735183f88..866b5442c 100644
--- a/src/protocol/packets/c2s.rs
+++ b/src/protocol/packets/c2s.rs
@@ -150,6 +150,27 @@ pub mod play {
             salt: u64,
             signature: Vec<u8>,
             signed_preview: bool,
+            acknowledgement: LastSeenMessageListAcknowledgement,
+        }
+    }
+
+    def_struct! {
+        LastSeenMessageList {
+            entries: Vec<LastSeenMessageListEntry>,
+        }
+    }
+
+    def_struct! {
+        LastSeenMessageListEntry {
+            profile_id: Uuid,
+            last_signature: Vec<u8>,
+        }
+    }
+
+    def_struct! {
+        LastSeenMessageListAcknowledgement {
+            last_seen: LastSeenMessageList,
+            last_received: Option<LastSeenMessageListEntry>
         }
     }