diff --git a/cfg/posix.cfg b/cfg/posix.cfg
index 76ea8d773..aee217c92 100644
--- a/cfg/posix.cfg
+++ b/cfg/posix.cfg
@@ -5498,4 +5498,9 @@ The function 'mktemp' is considered to be dangerous due to race conditions and s
   <define name="R_OK" value="4"/>
   <define name="W_OK" value="2"/>
   <define name="X_OK" value="1"/>
+  <!-- https://man7.org/linux/man-pages/man3/lockf.3.html -->
+  <define name="F_LOCK" value="1"/>
+  <define name="F_TEST" value="3"/>
+  <define name="F_TLOCK" value="2"/>
+  <define name="F_ULOCK" value="0"/>
 </def>