diff --git a/libc/kernel/uapi/linux/userfaultfd.h b/libc/kernel/uapi/linux/userfaultfd.h
index 46d7472..ad58fc0 100644
--- a/libc/kernel/uapi/linux/userfaultfd.h
+++ b/libc/kernel/uapi/linux/userfaultfd.h
@@ -19,6 +19,8 @@
 #ifndef _LINUX_USERFAULTFD_H
 #define _LINUX_USERFAULTFD_H
 #include <linux/types.h>
+#define USERFAULTFD_IOC 0xAA
+#define USERFAULTFD_IOC_NEW _IO(USERFAULTFD_IOC, 0x00)
 #define UFFD_API ((__u64) 0xAA)
 #define UFFD_API_REGISTER_MODES (UFFDIO_REGISTER_MODE_MISSING | UFFDIO_REGISTER_MODE_WP | UFFDIO_REGISTER_MODE_MINOR)
 #define UFFD_API_FEATURES (UFFD_FEATURE_PAGEFAULT_FLAG_WP | UFFD_FEATURE_EVENT_FORK | UFFD_FEATURE_EVENT_REMAP | UFFD_FEATURE_EVENT_REMOVE | UFFD_FEATURE_EVENT_UNMAP | UFFD_FEATURE_MISSING_HUGETLBFS | UFFD_FEATURE_MISSING_SHMEM | UFFD_FEATURE_SIGBUS | UFFD_FEATURE_THREAD_ID | UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM | UFFD_FEATURE_EXACT_ADDRESS | UFFD_FEATURE_WP_HUGETLBFS_SHMEM)