diff --git a/docs/users.rst b/docs/users.rst
index 4278c229..3a62dd4b 100644
--- a/docs/users.rst
+++ b/docs/users.rst
@@ -183,3 +183,7 @@ Limitations
 
 26. mmap() allows unlimited overcommit. Note that it corresponds to
     setting sysctl ``vm.overcommit_memory`` to 1.
+
+27. mlockall() is not supported and returns -EPERM.
+
+28. munlockall() is not supported and returns zero.