diff --git a/scripts/config.in b/scripts/config.in
index c6843783c..86a879a13 100644
--- a/scripts/config.in
+++ b/scripts/config.in
@@ -209,7 +209,7 @@ expert_begin
       choice ROCKCFG_PKGSEL_TPL none none 'No package preselection template' \
 		$( cd misc/pkgsel; grep -H "^# TITLE: " *.in | tr ' ' '_' | sed 's,\.in:#_TITLE:_, ,' )
       if [ -f misc/pkgsel/${ROCKCFG_PKGSEL_TPL}.in ]; then
-	cpp -Imisc/pkgsel/sets -imacros misc/pkgsel/macros -P misc/pkgsel/${ROCKCFG_PKGSEL_TPL}.in 2>/dev/null > config/$config.$swpid/predefined-pkgsel.parsed
+	cpp -undef -Imisc/pkgsel/sets -imacros misc/pkgsel/macros -P misc/pkgsel/${ROCKCFG_PKGSEL_TPL}.in 2>/dev/null > config/$config.$swpid/predefined-pkgsel.parsed
 	. config/$config.$swpid/predefined-pkgsel.parsed
       fi
       bool 'Custom package selection' ROCKCFG_PKGSEL 0
diff --git a/target/livecd/config.in b/target/livecd/config.in
index c0eaa7e9a..fe0bfeb95 100644
--- a/target/livecd/config.in
+++ b/target/livecd/config.in
@@ -61,7 +61,7 @@ ROCKCFGSET_PKG_LINUX_USE26MODTOOLS=1
 ROCKCFGSET_PKG_SUBVERSION_STATIC=0
 
 # hardwired for now...
-cpp -Imisc/pkgsel/sets -imacros misc/pkgsel/macros -P misc/pkgsel/minimal-desktop.in 2>/dev/null > config/$config.$swpid/predefined-pkgsel.parsed
+cpp -undef -Imisc/pkgsel/sets -imacros misc/pkgsel/macros -P misc/pkgsel/minimal-desktop.in 2>/dev/null > config/$config.$swpid/predefined-pkgsel.parsed
 . config/$config.$swpid/predefined-pkgsel.parsed
 
 pkgenable kiss