diff --git a/tests/sys/kern/kern_copyin.c b/tests/sys/kern/kern_copyin.c
index ed4225361ec3..b77360e928fd 100644
--- a/tests/sys/kern/kern_copyin.c
+++ b/tests/sys/kern/kern_copyin.c
@@ -66,6 +66,7 @@ get_maxuser_address(void)
 	mib[1] = KERN_PROC;
 	mib[2] = KERN_PROC_PS_STRINGS;
 	mib[3] = getpid();
+	len = sizeof(psstrings);
 	error = sysctl(mib, nitems(mib), &psstrings, &len, NULL, 0);
 	if (error != 0)
 		return (0);