diff --git a/fs/io_uring.c b/fs/io_uring.c
index f131105fa12a21ffce4f6245997f25d5b1a38cbe..4bbad2ed4ae34f69fd5acbf73bab218f724788e1 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -511,6 +511,9 @@ enum {
 	REQ_F_OVERFLOW_BIT,
 	REQ_F_POLLED_BIT,
 	REQ_F_BUFFER_SELECTED_BIT,
+
+	/* not a real bit, just to check we're not overflowing the space */
+	__REQ_F_LAST_BIT,
 };
 
 enum {
@@ -7998,6 +8001,7 @@ static int __init io_uring_init(void)
 	BUILD_BUG_SQE_ELEM(44, __s32,  splice_fd_in);
 
 	BUILD_BUG_ON(ARRAY_SIZE(io_op_defs) != IORING_OP_LAST);
+	BUILD_BUG_ON(__REQ_F_LAST_BIT >= 8 * sizeof(int));
 	req_cachep = KMEM_CACHE(io_kiocb, SLAB_HWCACHE_ALIGN | SLAB_PANIC);
 	return 0;
 };