Dear Gabriel, >Did you correctly run > > eval $(opam config en) I tried both (in a fresh shell). The effect is the same. A question for my understanding: I assumed that for building something inside of opam this is not required. I thought I need to do this only when I use ocaml to build something outside of opam. This also matches my (very limited) experience with opam. I try to find out what is going wrong here. Best regards, Michael From: Gabriel Scherer [mailto:gabriel.scherer@gmail.com] Sent: Saturday, June 25, 2016 5:37 PM To: Soegtrop, Michael Cc: caml-list@inria.fr Subject: Re: [Caml-list] Building ocamlbuild with opam fails after opam switch This is a bug, but I think it is likely to be coming from a misconfiguration on your end: the preinstalled test checks $(ocamlc -where)/ocamlbuild and if you are in a non-system switch this should not be /usr/local/lib/ocaml. Did you correctly run eval $(opam config en) after switching? On Sat, Jun 25, 2016 at 9:57 AM, Soegtrop, Michael > wrote: Dear OCaml Users, Opam works fine for me with the system installed OCaml, but after an opam switch I cannot build ocamlbuild or any package depending on it any more. Building ocamlbuild fails because it explicitly checks if there is already a system installed ocamlbuild: # ERROR: Preinstalled ocamlbuild detected at /usr/local/lib/ocaml/ocamlbuild # Installation aborted; if you want to bypass this safety check, pass CHECK_IF_PREINSTALLED=false to make # make: *** [Makefile:333: check-if-preinstalled] Error 2 Of cause I can just follow this advice and remove this check, but I wonder how others handle this. Best regards, Michael Intel Deutschland GmbH Registered Address: Am Campeon 10-12, 85579 Neubiberg, Germany Tel: +49 89 99 8853-0, www.intel.de Managing Directors: Christin Eisenschmid, Christian Lamprechter Chairperson of the Supervisory Board: Nicole Lau Registered Office: Munich Commercial Register: Amtsgericht Muenchen HRB 186928 Intel Deutschland GmbH Registered Address: Am Campeon 10-12, 85579 Neubiberg, Germany Tel: +49 89 99 8853-0, www.intel.de Managing Directors: Christin Eisenschmid, Christian Lamprechter Chairperson of the Supervisory Board: Nicole Lau Registered Office: Munich Commercial Register: Amtsgericht Muenchen HRB 186928