With OCaml >= 4.09 caml_named_value() returns a const value *, so keep the constness to build also in this case. Signed-off-by: Pino Toscano <ptoscano(a)redhat.com&gt; --- libvirt/libvirt_c_oneoffs.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/libvirt/libvirt_c_oneoffs.c b/libvirt/libvirt_c_oneoffs.c index 6f56f10..e23c0db 100644 --- a/libvirt/libvirt_c_oneoffs.c +++ b/libvirt/libvirt_c_oneoffs.c @@ -1207,7 +1207,7 @@ ocaml_libvirt_event_run_default_impl (value unitv) #define DOMAIN_CALLBACK_BEGIN(NAME) \ value connv, domv, callback_id, result; \ connv = domv = callback_id = result = Val_int(0); \ - static value *callback = NULL; \ + static const value *callback = NULL; \ caml_leave_blocking_section(); \ if (callback == NULL) \ callback = caml_named_value(NAME); \ @@ -1433,7 +1433,7 @@ timeout_callback(int timer, void *opaque) { value callback_id, result; callback_id = result = Val_int(0); - static value *callback = NULL; + static const value *callback = NULL; caml_leave_blocking_section(); if (callback == NULL) callback = caml_named_value("Libvirt.timeout_callback");