diff --git a/ocaml-lablgl.spec b/ocaml-lablgl.spec
index dbfb0cb..6f648da 100644
--- a/ocaml-lablgl.spec
+++ b/ocaml-lablgl.spec
@@ -1,15 +1,15 @@
+%global opt %(test -x %{_bindir}/ocamlopt && echo 1 || echo 0)
+
 Name:           ocaml-lablgl
 Epoch:          1
 Version:        1.05
-Release:        15%{?dist}
+Release:        16%{?dist}
 Summary:        LablGL is an OpenGL interface for Objective Caml
 License:        BSD
 
 URL:            http://forge.ocamlcore.org/projects/lablgl/
 Source0:        https://forge.ocamlcore.org/frs/download.php/1254/lablgl-%{version}.tar.gz
 
-# XXX This could be fixed with some changes to the build system:
-ExclusiveArch:  %{ocaml_native_compiler}
 
 BuildRequires:  freeglut-devel 
 BuildRequires:  ocaml >= 3.12.1-3
@@ -46,8 +46,13 @@ developing applications that use %{name}.
 %setup -q -n lablgl-%{version}
 
 cat > Makefile.config <<EOF
+%if %{opt}
 CAMLC = ocamlc.opt
 CAMLOPT = ocamlopt.opt -g
+%else
+CAMLC = ocamlc
+CAMLOPT = ocamlc -g
+%endif
 BINDIR = %{_bindir}
 XINCLUDES = -I%{_prefix}/X11R6/include
 XLIBS = -lXext -lXmu -lX11
@@ -67,7 +72,10 @@ EOF
 %build
 # Parallel builds don't work.
 unset MAKEFLAGS
-make all opt
+make all \
+%if %{opt}
+opt
+%endif
 
 
 %install
@@ -126,13 +134,18 @@ popd
 %doc CHANGES COPYRIGHT README LablGlut/examples Togl/examples
 %{_libdir}/ocaml/lablGL/META
 %{_libdir}/ocaml/lablGL/*.a
+%if %{opt}
 %{_libdir}/ocaml/lablGL/*.cmxa
 %{_libdir}/ocaml/lablGL/*.cmx
+%endif
 %{_libdir}/ocaml/lablGL/*.mli
 %{_libdir}/ocaml/lablGL/build.ml
 
 
 %changelog
+* Wed Jul 22 2015 Richard W.M. Jones <rjones@redhat.com> - 1:1.05-16
+- Fix bytecode builds (patch supplied by Rafael Fonseca).
+
 * Wed Jun 24 2015 Richard W.M. Jones <rjones@redhat.com> - 1:1.05-15
 - ocaml-4.02.2 final rebuild.