diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 6e52b67b420e7a3312f463f8d3bb6baad6576041..517e3719027e619e5c7b565d1de9294dfffb5a3c 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -1198,7 +1198,7 @@ static ssize_t psi_write(struct file *file, const char __user *user_buf,
 	if (static_branch_likely(&psi_disabled))
 		return -EOPNOTSUPP;
 
-	buf_size = min(nbytes, (sizeof(buf) - 1));
+	buf_size = min(nbytes, sizeof(buf));
 	if (copy_from_user(buf, user_buf, buf_size))
 		return -EFAULT;