diff --git a/Mk/bsd.lto.mk b/Mk/bsd.lto.mk
index f3b708a804a1..196f686f9a7c 100644
--- a/Mk/bsd.lto.mk
+++ b/Mk/bsd.lto.mk
@@ -1,11 +1,13 @@
 # LTO Support
+# This file enforces Link Time Optimization for ports.
+# In order to use it, add USE_LTO=yes to your /etc/make.conf.
 
 LTO_Include_MAINTAINER=	pkubaj@FreeBSD.org
 
 .if !defined(LTO_UNSAFE)
 # Overridable as a user may want to use -flto
 LTO_FLAGS?=	-flto=thin
 CFLAGS+=	${LTO_FLAGS}
 CXXFLAGS+=	${LTO_FLAGS}
 LDFLAGS+=	${LTO_FLAGS}
 .endif