diff --git a/libc/kernel/uapi/rdma/mlx5-abi.h b/libc/kernel/uapi/rdma/mlx5-abi.h
index aadb20e..f41c887 100644
--- a/libc/kernel/uapi/rdma/mlx5-abi.h
+++ b/libc/kernel/uapi/rdma/mlx5-abi.h
@@ -70,6 +70,7 @@
   MLX5_IB_ALLOC_UCONTEXT_RESP_MASK_ECE = 1UL << 2,
   MLX5_IB_ALLOC_UCONTEXT_RESP_MASK_SQD2RTS = 1UL << 3,
   MLX5_IB_ALLOC_UCONTEXT_RESP_MASK_REAL_TIME_TS = 1UL << 4,
+  MLX5_IB_ALLOC_UCONTEXT_RESP_MASK_MKEY_UPDATE_TAG = 1UL << 5,
 };
 enum mlx5_user_cmds_supp_uhw {
   MLX5_USER_CMDS_SUPP_UHW_QUERY_DEVICE = 1 << 0,