diff --git a/meta-security/README b/meta-security/README
index eb15366..4047b86 100644
--- a/meta-security/README
+++ b/meta-security/README
@@ -1,6 +1,24 @@
 Meta-security
 =============
 
+The bbappend files for some recipes (e.g. linux-yocto) in this layer need
+to have 'security' in DISTRO_FEATURES to have effect.
+To enable them, add in configuration file the following line.
+
+  DISTRO_FEATURES_append = " security"
+
+If meta-security is included, but security  is not enabled as a
+distro feature a warning is printed at parse time:
+
+    You have included the meta-security layer, but
+    'security' has not been enabled in your DISTRO_FEATURES. Some bbappend files
+    and preferred version setting may not take effect.
+
+If you know what you are doing, this warning can be disabled by setting the following
+variable in your configuration:
+
+  SKIP_META_SECURITY_SANITY_CHECK = 1
+
 This layer provides security tools, hardening tools for Linux kernels
 and libraries for implementing security mechanisms.