diff --git a/tests/sys/kern/ptrace_test.c b/tests/sys/kern/ptrace_test.c
index 694a3b4044e..a9afac55504 100644
--- a/tests/sys/kern/ptrace_test.c
+++ b/tests/sys/kern/ptrace_test.c
@@ -3474,7 +3474,7 @@ ATF_TC_BODY(ptrace__PT_STEP_with_signal, tc)
  * that restarting doesn't retrigger the breakpoint.
  */
 static void *
-continue_thread(void *arg)
+continue_thread(void *arg __unused)
 {
 	breakpoint();
 	return (NULL);