diff --git a/usr.bin/renice/tests/renice_test.sh b/usr.bin/renice/tests/renice_test.sh
--- a/usr.bin/renice/tests/renice_test.sh
+++ b/usr.bin/renice/tests/renice_test.sh
@@ -28,6 +28,7 @@
 # Name of user to use for -u tests when running as root.  Beware that
 # processes owned by that user will be affected by the test.
 TEST_USER=nobody
+SHELL=/bin/sh
 
 _renice() {
 	atf_check -o empty -e ignore -s exit:0 renice "$@"
@@ -97,7 +98,7 @@
 }
 renice_abs_user_body() {
 	local user pid nice incr
-	pid=$(su -m $TEST_USER -c "/bin/sh -c 'sleep 60 >/dev/null & echo \$!'")
+	pid=$(su -m $TEST_USER -c "sleep 60 >/dev/null & echo \$!")
 	nice="$(ps -o nice= -p $pid)"
 	incr=3
 	_renice $((nice+incr)) -u $TEST_USER
@@ -112,7 +113,7 @@
 }
 renice_rel_user_body() {
 	local user pid nice incr
-	pid=$(su -m $TEST_USER -c "/bin/sh -c 'sleep 60 >/dev/null & echo \$!'")
+	pid=$(su -m $TEST_USER -c "sleep 60 >/dev/null & echo \$!")
 	nice="$(ps -o nice= -p $pid)"
 	incr=3
 	_renice -u -n $incr $TEST_USER