diff --git a/specs/simple-serialize.md b/specs/simple-serialize.md
index a452213b5..a169f8f93 100644
--- a/specs/simple-serialize.md
+++ b/specs/simple-serialize.md
@@ -44,9 +44,9 @@ This is a **work in progress** describing typing, serialization and Merkleizatio
 
 For convenience we alias:
 
-* `byte` to `uint8`
-* `bytes` to `byte[]`
-* `bytesN` to `byte[N]`
+* `byte` to `uint8` (this is a basic type)
+* `bytes` to `byte[]` (this is *not* a basic type)
+* `bytesN` to `byte[N]` (this is *not* a basic type)
 
 ## Serialization