diff --git a/ruby.spec b/ruby.spec
index 6501c95..04b87f8 100644
--- a/ruby.spec
+++ b/ruby.spec
@@ -262,14 +262,7 @@ make DESTDIR=$RPM_BUILD_ROOT install
 cd ..
 
 # generate ri doc
-case %{_target_cpu} in
-	ppc|ppc64)
-		_cpu=%{_arch}
-		;;
-	*)
-		_cpu=%{_target_cpu}
-		;;
-esac
+_cpu=`echo %{_target_cpu} | sed 's/^ppc/powerpc/'`
 DESTDIR=$RPM_BUILD_ROOT LD_LIBRARY_PATH=$RPM_BUILD_ROOT%{_libdir} $RPM_BUILD_ROOT%{_bindir}/ruby -I $RPM_BUILD_DIR/%{name}-%{version}/%{name}-%{version} -I $RPM_BUILD_ROOT%{_libdir}/ruby/%{rubyxver}/$_cpu-%{_target_os}/ -I $RPM_BUILD_DIR/%{name}-%{version}/%{name}-%{version}/lib $RPM_BUILD_ROOT%{_bindir}/rdoc --all --ri-system $RPM_BUILD_DIR/%{name}-%{version}/%{name}-%{version}
 
 # XXX: installing irb