diff --git a/src/message.rs b/src/message.rs
index 939b3e1..9b02b92 100644
--- a/src/message.rs
+++ b/src/message.rs
@@ -260,10 +260,13 @@ impl<V: ?Sized + MessageValue> SerializedMessage<V>
 	    };
 	    (: $ser:expr) => {
 		{
-		    
+		    let ser = serde_cbor::to_vec($ser)?;
+		    write!(u64::try_from(ser.len())?.to_be_bytes());
+		    write!(ser);
+		    /*
 		    let mut w2 = WriteCounter(0, &mut writer);
 		    serde_cbor::to_writer(&mut w2, $ser)?;
-		    w+=w2.0;
+		    w+=w2.0;*/
 		}
 	    };
 	}
@@ -305,10 +308,18 @@ impl<V: ?Sized + MessageValue> SerializedMessage<V>
 		}
 	    };
 	    (: $ser:ty) => {
-		serde_cbor::from_reader::<$ser, _>(&mut reader).wrap_err(eyre!("Failed to deserialise {} from reader", std::any::type_name::<$ser>()))?
-	    };
-	    (:) => {
-		serde_cbor::from_reader(&mut reader).wrap_err(eyre!("Failed to deserialise type from reader"))?
+		{
+		    let mut len = [0u8; std::mem::size_of::<u64>()];
+		    read!(&mut len[..]);
+		    let len = usize::try_from(u64::from_be_bytes(len))?;
+		    //TODO: Find realistic max size for `$ser`.
+		    if len > MAX_ALLOC_SIZE {
+			return Err(eyre!("Invalid length read: {}", len));
+		    }
+		    let mut de = Vec::with_capacity(len);
+		    read!(&mut de, len);
+		    serde_cbor::from_slice::<$ser>(&de[..]).wrap_err(eyre!("Failed to deserialise {} from reader", std::any::type_name::<$ser>()))?
+		}
 	    };
 	    ($into:expr, $num:expr) => {
 		{