diff --git a/protocol.md b/protocol.md
index 7c9f03f..0b1eb51 100644
--- a/protocol.md
+++ b/protocol.md
@@ -1,11 +1,11 @@
 # tus resumable upload protocol
 
-**Version:** 1.0.0 ([SemVer](http://semver.org))<br>
+**Version:** 1.1.0 ([SemVer](http://semver.org))<br>
 **Date:** 2016-03-25<br>
 **Authors:** [Felix Geisendörfer](https://twitter.com/felixge), [Kevin van
 Zonneveld](https://twitter.com/kvz), [Tim Koschützki](https://twitter.com/tim_kos),
 [Naren Venkataraman](https://github.com/vayam), [Marius
-Kleidl](https://twitter.com/Acconut_)<br>
+Kleidl](https://twitter.com/Acconut_), [Ben Stahl](https://github.com/bhstahl)<br>
 **Collaborators**:
 [Bruno de Carvalho](https://github.com/biasedbit),
 [James Butler](https://github.com/sandfox),
@@ -210,6 +210,9 @@ bytes contained in the message at the given offset specified by the
 `Upload-Offset` header. All `PATCH` requests MUST use
 `Content-Type: application/offset+octet-stream`.
 
+If the `Upload-Offset` or `Content-Type` headers are invalid or missing from the
+request, the Server MUST return `412 Precondition Failed`.
+
 The `Upload-Offset` header's value MUST be equal to the current offset of the
 resource. In order to achieve parallel upload the
 [Concatenation](#concatenation) extension MAY be used. If the offsets do not
@@ -338,6 +341,9 @@ Once set the length MUST NOT be changed. As long as the length of the upload is
 not known, the Server MUST set `Upload-Defer-Length: 1` in all responses to
 `HEAD` requests.
 
+If the `Upload-Length` or `Upload-Defer-Length` headers are missing from the
+request, the Server MUST return `412 Precondition Failed`.
+
 If the Server supports deferring length, it MUST add `creation-defer-length` to
 the `Tus-Extension` header.