diff --git a/ocaml-curses.spec b/ocaml-curses.spec
index 38b1c66..d392648 100644
--- a/ocaml-curses.spec
+++ b/ocaml-curses.spec
@@ -34,6 +34,7 @@ BuildRequires:  ncurses-devel
 BuildRequires:  ocaml >= 4.00.1
 BuildRequires:  ocaml-rpm-macros >= 4.02.1
 BuildRequires:  ocaml-findlib-devel >= 1.3.3-3
+BuildRequires:  ocaml(ocaml.opt)
 BuildRoot:      %{_tmppath}/%{name}-%{version}-build
 
 %description
@@ -60,8 +61,9 @@ autoreconf
 
 
 %build
+# Parallel builds don't work (with bytecode)
 %configure --enable-widec
-make %{?_smp_mflags} all opt
+make all opt
 
 
 %install
@@ -69,7 +71,11 @@ make %{?_smp_mflags} all opt
 export DESTDIR=%{buildroot}
 export OCAMLFIND_DESTDIR=%{buildroot}%{_libdir}/ocaml
 mkdir -p $OCAMLFIND_DESTDIR $OCAMLFIND_DESTDIR/stublibs
-ocamlfind install curses META *.cmi *.cmx *.cma *.cmxa *.a *.so *.mli
+export OCAMLFILES="curses META *.cmi *.cma *.so *.mli"
+%if %{ocaml_native_compiler}
+export OCAMLFILES="$OCAMLFILES *.cmx *.cmxa *.a"
+%endif
+ocamlfind install $OCAMLFILES