diff --git a/ORBit2.spec b/ORBit2.spec
index 4dc479c..4dcbc1c 100644
--- a/ORBit2.spec
+++ b/ORBit2.spec
@@ -4,7 +4,7 @@
 Summary: A high-performance CORBA Object Request Broker
 Name: ORBit2
 Version: 2.14.19
-Release: 9%{?dist}
+Release: 10%{?dist}
 #VCS: git:git://git.gnome.org/ORBit2
 Source: http://download.gnome.org/sources/ORBit2/2.14/%{name}-%{version}.tar.bz2
 Group: System Environment/Daemons
@@ -81,11 +81,7 @@ rm -f $RPM_BUILD_ROOT%{_libdir}/ORBit-2.0/*.*a
 rm -f $RPM_BUILD_ROOT%{_libdir}/orbit-2.0/*.*a
 
 # fix multilib conflict caused by orbit-config.h
-%ifarch x86_64 s390x ia64 ppc64 alpha sparc64
-%define wordsize 64
-%else
-%define wordsize 32
-%endif
+%define wordsize %{_isa_bits}
 
 mv $RPM_BUILD_ROOT%{_includedir}/orbit-2.0/orbit/orbit-config.h \
    $RPM_BUILD_ROOT%{_includedir}/orbit-2.0/orbit/orbit-config-%{wordsize}.h
@@ -135,6 +131,9 @@ EOF
 %{_datadir}/gtk-doc
 
 %changelog
+* Thu Dec  5 2013 Peter Robinson <pbrobinson@fedoraproject.org> 2.14.19-10
+- Simplify wordsize definition (fix FTBFS on aarch64)
+
 * Fri Aug 02 2013 Fedora Release Engineering <rel-eng@lists.fedoraproject.org> - 2.14.19-9
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_20_Mass_Rebuild