diff --git a/man2/mlock.2 b/man2/mlock.2
index b8487ff29..8f4837290 100644
--- a/man2/mlock.2
+++ b/man2/mlock.2
@@ -170,6 +170,15 @@ was not a multiple of the page size.
 .B ENOMEM
 Some of the specified address range does not correspond to mapped
 pages in the address space of the process.
+.TP
+.B ENOMEM
+Locking or unlocking a region would result in the total number of
+mappings with distinct attributes (e.g., locked versus unlocked)
+exceeding the allowed maximum.
+.\" I.e., the number of VMAs would exceed the 64kB maximum
+(For example, unlocking a range in the middle of a currently locked
+mapping would result in three mappings:
+two locked mappings at each end and an unlocked mapping in the middle.)
 .LP
 For
 .BR mlockall ():