diff --git a/tests/sched_test.cpp b/tests/sched_test.cpp
index 92d6c26..a4cffc0 100644
--- a/tests/sched_test.cpp
+++ b/tests/sched_test.cpp
@@ -55,7 +55,8 @@
   // Check that our hand-written clone assembler sets errno correctly on failure.
   uintptr_t fake_child_stack[16];
   errno = 0;
-  ASSERT_EQ(-1, clone(NULL, &fake_child_stack[16], CLONE_THREAD, NULL));
+  // If CLONE_THREAD is set, CLONE_SIGHAND must be set too.
+  ASSERT_EQ(-1, clone(child_fn, &fake_child_stack[16], CLONE_THREAD, NULL));
   ASSERT_EQ(EINVAL, errno);
 }