diff --git a/t/t2000-checkout-cache-clash.sh b/t/t2000-checkout-cache-clash.sh
index 5141fab..f7e1a73 100755
--- a/t/t2000-checkout-cache-clash.sh
+++ b/t/t2000-checkout-cache-clash.sh
@@ -38,7 +38,7 @@
 
 test_expect_success \
     'git checkout-index without -f should fail on conflicting work tree.' \
-    '! git checkout-index -a'
+    'test_must_fail git checkout-index -a'
 
 test_expect_success \
     'git checkout-index with -f should succeed.' \