diff --git a/t/test-lib.sh b/t/test-lib.sh
index 285bfd8943..dbb13af33e 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -598,6 +598,9 @@ test_must_fail () {
 	elif test $exit_code -gt 129 -a $exit_code -le 192; then
 		echo >&2 "test_must_fail: died by signal: $*"
 		return 1
+	elif test $exit_code = 127; then
+		echo >&2 "test_must_fail: command not found: $*"
+		return 1
 	fi
 	return 0
 }