diff --git a/packages/datalog/datalog.0.6/opam b/packages/datalog/datalog.0.6/opam
index cfe60767156..7eda84c046a 100644
--- a/packages/datalog/datalog.0.6/opam
+++ b/packages/datalog/datalog.0.6/opam
@@ -9,7 +9,7 @@ doc: "https://c-cube.github.io/datalog"
 bug-reports: "https://github.com/c-cube/datalog/issues"
 depends: [
   "dune"
-  "ocaml" {>= "4.03"}
+  "ocaml" {>= "4.03" & < "5.0"}
   "odoc" {with-doc}
   "mdx" {>= "1.3" & with-test}
 ]
@@ -26,4 +26,4 @@ url {
     "md5=4a2d12d630a5edd694968675a84a3ef5"
     "sha512=685c0e186705837cb3ac66df6e8011d9f6a9629484b3a813b767df95348d5a41f37301f3e199ed6c91a42a87d1563e8355377269176785b123eb297a5ad022d7"
   ]
-}
\ No newline at end of file
+}