diff --git a/quinn-proto/src/packet.rs b/quinn-proto/src/packet.rs
index d6f6c8ca7..f0f9f4f8f 100644
--- a/quinn-proto/src/packet.rs
+++ b/quinn-proto/src/packet.rs
@@ -514,7 +514,11 @@ impl PlainHeader {
         let first = buf.get::<u8>()?;
         if first & LONG_HEADER_FORM == 0 {
             let spin = first & SPIN_BIT != 0;
-            let dst_cid = ConnectionId::new(&buf.bytes()[..local_cid_len]);
+            let dst_cid = ConnectionId::new(
+                &buf.bytes()
+                    .get(..local_cid_len)
+                    .ok_or(PacketDecodeError::InvalidHeader("cid out of bounds"))?,
+            );
             buf.advance(local_cid_len);
 
             Ok(PlainHeader::Short {