diff --git a/spec.md b/spec.md
index 1ea5bc5e..649ec64e 100644
--- a/spec.md
+++ b/spec.md
@@ -328,7 +328,8 @@ OCI-Chunk-Min-Length: <size>
 Please reference the above section for restrictions on the `<location>`.
 
 ---
-To upload a chunk, issue a `PATCH` request to a URL path in the following format, and with the following headers and body:
+To upload a chunk, issue a `PATCH` request to a URL path in the following format, and with the following headers and body.
+`Content-Length` can be omitted if HTTP chunked transfer encoding is used:
 
 URL path: `<location>` <sup>[end-5](#endpoints)</sup>
 ```