diff --git a/.travis.yml b/.travis.yml
index a045d4b..6aec0e6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,5 +4,6 @@ install:
   - wget https://raw.githubusercontent.com/simonjbeaumont/ocaml-travis-coveralls/master/travis-coveralls.sh
 dist: trusty
 script: bash -ex .travis-opam.sh && bash -ex travis-coveralls.sh
+sudo: required
 env:
   - OCAML_VERSION=4.02
diff --git a/lib/block.mli b/lib/block.mli
index 8d38466..fe6917c 100644
--- a/lib/block.mli
+++ b/lib/block.mli
@@ -19,7 +19,6 @@
 include V1.BLOCK
 with type 'a io = 'a Lwt.t
 and type     page_aligned_buffer = Cstruct.t
-and type     id = string
 
 (** {0} low-level convenience functions *)