diff --git a/aarch64/run_gdb.sh b/aarch64/run_gdb.sh
index 2555d13..6210c8a 100755
--- a/aarch64/run_gdb.sh
+++ b/aarch64/run_gdb.sh
@@ -42,7 +42,7 @@
 		exit 0
 		;;
 	\?)
-		echo "Invalid option: ${!OPTIND}" 1>&2
+		echo "Invalid option: -${OPTARG}" 1>&2
 		usage 1>&2
 		exit 1
 		;;
diff --git a/aarch64/run_qemu.sh b/aarch64/run_qemu.sh
index d628518..58d7b5a 100755
--- a/aarch64/run_qemu.sh
+++ b/aarch64/run_qemu.sh
@@ -130,7 +130,7 @@
 		exit 0
 		;;
 	\?)
-		echo "Invalid option: ${!OPTIND}" 1>&2
+		echo "Invalid option: -${OPTARG}" 1>&2
 		usage 1>&2
 		exit 1
 		;;
diff --git a/kvm-unit-tests/run_test.sh b/kvm-unit-tests/run_test.sh
index b38d5cc..3f5a95f 100755
--- a/kvm-unit-tests/run_test.sh
+++ b/kvm-unit-tests/run_test.sh
@@ -68,7 +68,7 @@
 		exit 0
 		;;
 	\?)
-		echo "Invalid option: ${!OPTIND}" 1>&2
+		echo "Invalid option: -${OPTARG}" 1>&2
 		usage 1>&2
 		exit 1
 		;;