diff --git a/man4/mem.4 b/man4/mem.4
index b16ca64a0..b1bb21832 100644
--- a/man4/mem.4
+++ b/man4/mem.4
@@ -23,7 +23,7 @@
 .\" %%%LICENSE_END
 .\"
 .\" Modified Sat Jul 24 16:59:10 1993 by Rik Faith (faith@cs.unc.edu)
-.TH MEM 4 1992-11-21 "Linux" "Linux Programmer's Manual"
+.TH MEM 4 2015-01-02 "Linux" "Linux Programmer's Manual"
 .SH NAME
 mem, kmem, port \- system memory, kernel memory and system ports
 .SH DESCRIPTION
@@ -40,6 +40,13 @@ References to nonexistent locations cause errors to be returned.
 Examining and patching is likely to lead to unexpected results
 when read-only or write-only bits are present.
 .LP
+Since 2.6.26, and depending on the architecture, the
+.B CONFIG_STRICT_DEVMEM
+kernel configuration option limits the areas
+which can be accessed through this file.
+For example: on x86, RAM access is not allowed but accessing
+memory-mapped PCI regions is.
+.LP
 It is typically created by:
 .RS
 .sp