diff --git a/build_rpm.in b/build_rpm.in
index b203473b..7cc66e21 100755
--- a/build_rpm.in
+++ b/build_rpm.in
@@ -35,12 +35,13 @@ if ! test -z "$2"; then
     RESULTS=/tmp/nexus-mock-results
     mkdir -p $RESULTS
     mock_args="-r $2 --resultdir=$RESULTS"
+    rm -f $RESULTS/*.src.rpm # clean up so do not pick up wrong .src.rpm later
     mock ${mock_args} --init
-    env NEXUS_CONFIG_OPTIONS="$build_args" mock ${mock_args} --buildsrpm --spec nexus.spec --sources . --define "_source_filedigest_algorithm md5" --define "_binary_filedigest_algorithm md5" 
+    mock ${mock_args} --buildsrpm --spec nexus.spec --sources . --define "nexus_config_options $build_args" --define "_source_filedigest_algorithm md5" --define "_binary_filedigest_algorithm md5" 
     srpm=`ls $RESULTS/*.src.rpm`
-    env NEXUS_CONFIG_OPTIONS="$build_args" mock ${mock_args} --rebuild $srpm  --define "_source_filedigest_algorithm md5" --define "_binary_filedigest_algorithm md5"
+    mock ${mock_args} --rebuild $srpm --define "nexus_config_options $build_args" --define "_source_filedigest_algorithm md5" --define "_binary_filedigest_algorithm md5"
 else
 # buildroot is actually where we install to
     cd $topdir/SPECS
-    env NEXUS_CONFIG_OPTIONS="$build_args" rpmbuild -ba --buildroot $nxtop/installroot --define "_source_filedigest_algorithm md5" --define "_binary_filedigest_algorithm md5" nexus.spec
+    rpmbuild -ba --buildroot $nxtop/installroot --define "nexus_config_options $build_args" --define "_source_filedigest_algorithm md5" --define "_binary_filedigest_algorithm md5" nexus.spec
 fi
diff --git a/nexus_spec.in b/nexus_spec.in
index 744e9cb2..951677b2 100644
--- a/nexus_spec.in
+++ b/nexus_spec.in
@@ -38,16 +38,34 @@ Packager: NeXus Developers <nexus-developers@nexusformat.org>
 %define is_rhel5 1
 %endif
 
+%if 0%{?rhel} == 6
+%define is_rhel6 1
+%endif
+%if 0%{?el6}
+%define is_rhel6 1
+%endif
+%if "0%{?dist}" == "0.el6"
+%define is_rhel6 1
+%endif
+
 BuildRoot: %{_tmppath}/@PACKAGE_TARNAME@-@PACKAGE_VERSION@
 BuildRequires: python numpy
 BuildRequires: hdf5-devel hdf-devel 
+BuildRequires: libxml2-devel
+BuildRequires: java-1.6.0-openjdk-devel
+BuildRequires: readline-devel
 # mxml is not in rhel or epel as yet
+# ant on rhel5 is too old to build NXvalidate
 %if 0%{?fedora}
 BuildRequires: mxml-devel
+BuildRequires: ant
 %endif
 %if 0%{?is_rhel5}
 BuildRequires: python-ctypes
 %endif
+%if 0%{?is_rhel6}
+BuildRequires: ant ant-nodeps
+%endif
 
 %description
 NeXus is an international standard for exchanging data files
@@ -107,9 +125,9 @@ data is stored using the HDF format from NCSA. This package provides
 # RPM_INSTALL_PREFIX - where to install software
 # do --prefix last in case also present in passed config options
 if ! test -z "$RPM_INSTALL_PREFIX"; then
-    ./configure $NEXUS_CONFIG_OPTIONS --prefix="$RPM_INSTALL_PREFIX"
+    ./configure %{?nexus_config_options} --prefix="$RPM_INSTALL_PREFIX"
 else
-    ./configure $NEXUS_CONFIG_OPTIONS --prefix=%{_prefix} --libdir=%{_libdir}
+    ./configure %{?nexus_config_options} --prefix=%{_prefix} --libdir=%{_libdir}
 fi
 make