diff --git a/lib_protocol_compiler/tezos-protocol-compiler.opam b/lib_protocol_compiler/tezos-protocol-compiler.opam
index 77530f471..bd2aaf5cd 100644
--- a/lib_protocol_compiler/tezos-protocol-compiler.opam
+++ b/lib_protocol_compiler/tezos-protocol-compiler.opam
@@ -22,3 +22,5 @@ build: [
 build-test: [
   [ "jbuilder" "runtest" "-p" name "-j" jobs ]
 ]
+## ocaml-version should be in sync with `script/version.sh`
+available: [ ocaml-version = "4.04.2" ]
\ No newline at end of file
diff --git a/scripts/version.sh b/scripts/version.sh
index 3562063ff..5e6df0574 100644
--- a/scripts/version.sh
+++ b/scripts/version.sh
@@ -1,4 +1,7 @@
 #! /bin/sh
 
+## `ocaml-verions` should be in sync with
+## `lib.protocol-compiler/tezos-protocol-compiler.opam`
+
 alpine_version=3.6
 ocaml_version=4.04.2