diff --git a/tests/4-opt/test_perf.sh b/tests/4-opt/test_perf.sh
index 25581f9a268dd67073c9c7b26fcba67911be155a..bcd321302d4370eccb93826f23959a9327fe8fab 100755
--- a/tests/4-opt/test_perf.sh
+++ b/tests/4-opt/test_perf.sh
@@ -22,7 +22,7 @@ check_return_value() {
 
 usage() {
 	cat <<JIANMU
-Usage: $0 test-type
+Usage: $0 [test-type]
 test-type: 'licm' or 'mem2reg'
 JIANMU
 	exit 0