diff --git a/libc-test/build.rs b/libc-test/build.rs
index 226757c6ad8dc..deb3ca4e456b2 100644
--- a/libc-test/build.rs
+++ b/libc-test/build.rs
@@ -1939,6 +1939,7 @@ fn test_freebsd(target: &str) {
                 "sys/ucontext.h",
                 "sys/uio.h",
                 "sys/ktrace.h",
+                "sys/umtx.h",
                 "sys/un.h",
                 "sys/user.h",
                 "sys/utsname.h",
diff --git a/libc-test/semver/freebsd.txt b/libc-test/semver/freebsd.txt
index cfb0ef8beab00..f1ce1b571ae93 100644
--- a/libc-test/semver/freebsd.txt
+++ b/libc-test/semver/freebsd.txt
@@ -1240,6 +1240,7 @@ UF_REPARSE
 UF_SETTABLE
 UF_SPARSE
 UF_SYSTEM
+UMTX_ABSTIME
 UMTX_OP_WAIT
 UMTX_OP_WAKE
 UMTX_OP_MUTEX_TRYLOCK
diff --git a/src/unix/bsd/freebsdlike/freebsd/mod.rs b/src/unix/bsd/freebsdlike/freebsd/mod.rs
index ed9afabeaac5d..c71e7bdc4be2b 100644
--- a/src/unix/bsd/freebsdlike/freebsd/mod.rs
+++ b/src/unix/bsd/freebsdlike/freebsd/mod.rs
@@ -1198,6 +1198,12 @@ s_no_extra_traits! {
         pub ifdr_vendor: u32,
         pub ifdr_msg: [::c_char; ::IFDR_MSG_SIZE as usize],
     }
+
+    pub struct _umtx_time {
+        pub _timeout: ::timespec,
+        pub _flags: u32,
+        pub _clockid: u32,
+    }
 }
 
 cfg_if! {
@@ -3682,6 +3688,8 @@ pub const UMTX_OP_SEM2_WAKE: ::c_int = 24;
 pub const UMTX_OP_SHM: ::c_int = 25;
 pub const UMTX_OP_ROBUST_LISTS: ::c_int = 26;
 
+pub const UMTX_ABSTIME: u32 = 1;
+
 const_fn! {
     {const} fn _ALIGN(p: usize) -> usize {
         (p + _ALIGNBYTES) & !_ALIGNBYTES