diff --git a/tdb.spec b/tdb.spec
index 2205c27..39bd342 100644
--- a/tdb.spec
+++ b/tdb.spec
@@ -17,8 +17,8 @@
 
 # norootforbuild
 
-%if "%{python_sitearch}" == ""
-# CentOS and RHEL pre-6 don't know python_sitearch
+%if %{undefined python_sitearch}
+## CentOS and RHEL pre-6 don't know python_sitearch
 %define python_sitearch %(%{__python} -c "from distutils.sysconfig import get_python_lib; import sys; sys.stdout.write(get_python_lib(1))")
 %endif