diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 22e6e45af0a..cae82e79cef 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -7113,7 +7113,9 @@ with pkgs;
 
   opaline = callPackage ../development/tools/ocaml/opaline { };
 
-  opam = callPackage ../development/tools/ocaml/opam { };
+  opam = callPackage ../development/tools/ocaml/opam {
+    inherit (ocaml-ng.ocamlPackages_4_05) ocaml;
+  };
 
   picat = callPackage ../development/compilers/picat {
     stdenv = overrideCC stdenv gcc49;