diff --git a/BinaryEncoding.md b/BinaryEncoding.md
index 57bd1a8f..342df9c7 100644
--- a/BinaryEncoding.md
+++ b/BinaryEncoding.md
@@ -53,6 +53,15 @@ represented by _at most_ ceil(_N_/7) bytes that may contain padding `0x80` or `0
 
 Note: Currently, the only sizes used are `varint7`, `varint32` and `varint64`.
 
+### Non-canonical LEB128
+
+Both `varuintN` and `varintN` can be encoded with *non-canonical* LEB128 values where:
+
+* non-relevant zero `0x80` bytes are present in an over-large encoding; and / or
+* non-relevant LEB128 bits (bits past the size) are ignored.
+
+The total number of bytes used to encode the `varuintN` / `varintN` cannot exceed the largest *canonical* encoding for that `varuintN` / `varintN`.
+
 ## Language Types
 
 All types are distinguished by a negative `varint7` values that is the first byte of their encoding (representing a type constructor):