diff --git a/buds/01.md b/buds/01.md
index 146717f..f3bed29 100644
--- a/buds/01.md
+++ b/buds/01.md
@@ -10,6 +10,10 @@ _All pubkeys MUST be in hex format_
 
 Servers MUST set the `Access-Control-Allow-Origin: *`, `Access-Control-Allow-Headers: Authorization,*` and `Access-Control-Allow-Methods: GET, PUT, DELETE` headers on all endpoints to ensure compatibility with apps hosted on other domains
 
+## Error responses
+
+Every time a server sends an error response (HTTP status codes >=400), it may include a human-readable header `X-Reason` that can be displayed to the user.
+
 ## Authorization events
 
 Authorization events are used to identify the users to the server
diff --git a/buds/06.md b/buds/06.md
index c587032..739404b 100644
--- a/buds/06.md
+++ b/buds/06.md
@@ -8,14 +8,13 @@ Defines how clients can verify if the upload can be completed before sending the
 
 ## HEAD /upload - Upload requirements
 
-The `HEAD /upload` endpoint `MUST` use the `X-SHA-256`, `X-Content-Type` and `X-Content-Length` headers sent by client to get the SHA-256 hash, MIME type and size of the blob that will be uploaded, returning a HTTP status code and a custom header `X-Upload-Message` to indicate some human readable message about the upload requirements.
+The `HEAD /upload` endpoint `MUST` use the `X-SHA-256`, `X-Content-Type` and `X-Content-Length` headers sent by client to get the SHA-256 hash, MIME type and size of the blob that will be uploaded, returning a HTTP status code and a custom header `X-Reason` to indicate some human readable message about the upload requirements.
 
 ### Headers
 
 - `X-SHA-256`: A string that represents the blob's SHA-256 hash.
 - `X-Content-Length`: An integer that represents the blob size in bytes.
 - `X-Content-Type`: A string that specifies the blob's MIME type, like `application/pdf` or `image/png`.
-- `X-Upload-Message`: A human readable message that explains the reason why the upload cannot proceed.
 
 ### Upload Authorization
 
@@ -39,36 +38,36 @@ Example response from the server if the upload can be done:
 HTTP/1.1 200 OK
 ```
 
-If the upload cannot proceed, the server `MUST` return an appropriate `4xx` HTTP status code and a custom header `X-Upload-Message` with a human readable error message.
+If the upload cannot proceed, the server `MUST` return an appropriate `4xx` HTTP status code and a custom header `X-Reason` with a human readable error message.
 
 Some examples of error messages:
 
 ```http
 HTTP/1.1 400 Bad Request
-X-Upload-Message: Invalid X-SHA-256 header format. Expected a string.
+X-Reason: Invalid X-SHA-256 header format. Expected a string.
 ```
 
 ```http
 HTTP/1.1 401 Unauthorized
-X-Upload-Message: Authorization required for uploading video files.
+X-Reason: Authorization required for uploading video files.
 ```
 
 ```http
 HTTP/1.1 403 Forbidden
-X-Upload-Message: SHA-256 hash banned.
+X-Reason: SHA-256 hash banned.
 ```
 
 ```http
 HTTP/1.1 411 Length Required
-X-Upload-Message: Missing X-Content-Length header.
+X-Reason: Missing X-Content-Length header.
 ```
 
 ```http
 HTTP/1.1 413 Content Too Large
-X-Upload-Message: File too large. Max allowed size is 100MB.
+X-Reason: File too large. Max allowed size is 100MB.
 ```
 
 ```http
 HTTP/1.1 415 Unsupported Media Type
-X-Upload-Message: Unsupported file type.
+X-Reason: Unsupported file type.
 ```