diff --git a/bootstrap b/bootstrap
index f65e2aa5c..147e82567 100755
--- a/bootstrap
+++ b/bootstrap
@@ -1,7 +1,8 @@
 #! /bin/sh
 cd `dirname $0`
 # Check libtoolize version, fix for Debian/Woody
-if [ -x `which libtoolize` ]; then
+lt=`which libtoolize`
+if [ -n "$lt" -a -x "$lt" ]; then
 	LTIZE_VER=`libtoolize --version | head -1 | sed 's/^[^0-9]*//'`
 	LTIZE_VER_MAJOR=`echo $LTIZE_VER | cut -f1 -d'.'`
 	LTIZE_VER_MINOR=`echo $LTIZE_VER | cut -f2 -d'.'`
@@ -12,7 +13,8 @@ if [ -x `which libtoolize` ]; then
 fi
 
 # Check Autoconf version
-if [ -x `which autoconf` ]; then
+ac=`which autoconf`
+if [ -n "$ac" -a -x "$ac" ]; then
 	AC_VER=`autoconf --version | head -1 | sed 's/^[^0-9]*//'`
 	AC_VER_MAJOR=`echo $AC_VER | cut -f1 -d'.'`
 	AC_VER_MINOR=`echo $AC_VER | cut -f2 -d'.' | sed 's/[^0-9]*$//'`