diff --git a/prll.sh b/prll.sh
index 2ed4c04..bcf1525 100644
--- a/prll.sh
+++ b/prll.sh
@@ -25,13 +25,13 @@ function prll() {
 	EOF
 	return 1
     fi
-    /usr/bin/which prll_jobserver > /dev/null
+    @GENTOO_PORTAGE_EPREFIX@/usr/bin/which prll_jobserver > /dev/null
     if [[ $? -ne 0 ]] ; then
 	echo "PRLL: Missing prll_jobserver." 1>&2
 	return 1
     fi
     if [[ -z $PRLL_NR_CPUS ]] ; then
-	/usr/bin/which grep > /dev/null
+	@GENTOO_PORTAGE_EPREFIX@/usr/bin/which grep > /dev/null
 	if [[ $? -ne 0 || ! -a /proc/cpuinfo ]] ; then
 	    echo "PRLL: Environment variable PRLL_NR_CPUS is not set" 1>&2
 	    echo "PRLL: and either the grep utility is missing or" 1>&2