diff --git a/packages/ptset/ptset.1.0.0/opam b/packages/ptset/ptset.1.0.0/opam
index 331295702c3..cda0543dbf8 100644
--- a/packages/ptset/ptset.1.0.0/opam
+++ b/packages/ptset/ptset.1.0.0/opam
@@ -16,7 +16,7 @@ remove: [
   ["ocamlfind" "remove" "ptset"]
 ]
 depends: [
-  "ocaml"
+  "ocaml" {< "4.05.0"}
   "ocamlfind"
   "obuild" {build}
 ]