diff --git a/CHANGES.md b/CHANGES.md
index 01a807d7..6b61345e 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,7 @@
+# 0.18.1
+
+* Add an upper bound for Cohttp. Opium is only compatible with Cohttp < 3.0.
+
 # 0.18.0
 
 * Make examples easier to find and add documentation related to features used in them. (#125, @shonfeder)
diff --git a/README.md b/README.md
index f321226e..9be90a5e 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,8 @@
 Opium
 =====
 
+**Warning:** This branch is for the Cohttp version of Opium. It is in maintenance mode and every new feature will be added in the Httpaf-based version of Opium (version 0.19.0 and above).
+
 ## Executive Summary
 
 Sinatra like web toolkit for OCaml based on [cohttp](https://github.com/mirage/ocaml-cohttp/) & [lwt](https://github.com/ocsigen/lwt)
diff --git a/dune-project b/dune-project
index 15955d8e..cbd7889c 100644
--- a/dune-project
+++ b/dune-project
@@ -28,8 +28,8 @@
   (dune
    (>= 1.11))
   hmap
-  cohttp
-  cohttp-lwt
+  (cohttp (< 3.0))
+  (cohttp-lwt (< 3.0))
   lwt
   fieldslib
   sexplib
@@ -49,7 +49,7 @@
   (dune
    (>= 1.11))
   opium_kernel
-  cohttp-lwt-unix
+  (cohttp-lwt-unix (< 3.0))
   ezjsonm
   lwt
   logs
diff --git a/opium.opam b/opium.opam
index 3a7306da..423ebefe 100644
--- a/opium.opam
+++ b/opium.opam
@@ -18,7 +18,7 @@ depends: [
   "ocaml" {>= "4.04.1"}
   "dune" {>= "1.11"}
   "opium_kernel"
-  "cohttp-lwt-unix"
+  "cohttp-lwt-unix" {< "3.0"}
   "ezjsonm"
   "lwt"
   "logs"
diff --git a/opium_kernel.opam b/opium_kernel.opam
index 4317fb88..60f3cb10 100644
--- a/opium_kernel.opam
+++ b/opium_kernel.opam
@@ -13,8 +13,8 @@ depends: [
   "ocaml" {>= "4.04.1"}
   "dune" {>= "1.11"}
   "hmap"
-  "cohttp"
-  "cohttp-lwt"
+  "cohttp" {< "3.0"}
+  "cohttp-lwt" {< "3.0"}
   "lwt"
   "fieldslib"
   "sexplib"