diff --git a/libc/kernel/uapi/linux/membarrier.h b/libc/kernel/uapi/linux/membarrier.h
index 43c103b..94dd797 100644
--- a/libc/kernel/uapi/linux/membarrier.h
+++ b/libc/kernel/uapi/linux/membarrier.h
@@ -29,6 +29,7 @@
   MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE = (1 << 6),
   MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ = (1 << 7),
   MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ = (1 << 8),
+  MEMBARRIER_CMD_GET_REGISTRATIONS = (1 << 9),
   MEMBARRIER_CMD_SHARED = MEMBARRIER_CMD_GLOBAL,
 };
 enum membarrier_cmd_flag {