diff --git a/share/man/man5/src.conf.5 b/share/man/man5/src.conf.5
index 37fb5ef571c1..c62a6d605615 100644
--- a/share/man/man5/src.conf.5
+++ b/share/man/man5/src.conf.5
@@ -1,6 +1,6 @@
 .\" DO NOT EDIT-- this file is @generated by tools/build/options/makeman.
 .\" $FreeBSD$
-.Dd October 25, 2018
+.Dd October 30, 2018
 .Dt SRC.CONF 5
 .Os
 .Sh NAME
@@ -659,6 +659,8 @@ An alternate bootstrap tool chain must be provided.
 .It Va WITHOUT_EXAMPLES
 Set to avoid installing examples to
 .Pa /usr/share/examples/ .
+.It Va WITH_EXPERIMENTAL
+Set to include experimental features in the build.
 .It Va WITH_EXTRA_TCP_STACKS
 Set to build extra TCP stack modules.
 .It Va WITHOUT_FDT
diff --git a/share/mk/src.opts.mk b/share/mk/src.opts.mk
index 7091db36459f..10aa1e8986ac 100644
--- a/share/mk/src.opts.mk
+++ b/share/mk/src.opts.mk
@@ -197,6 +197,7 @@ __DEFAULT_NO_OPTIONS = \
     BSD_GREP \
     CLANG_EXTRAS \
     DTRACE_TESTS \
+    EXPERIMENTAL \
     GNU_GREP_COMPAT \
     HESIOD \
     LIBSOFT \
diff --git a/sys/conf/options b/sys/conf/options
index 2519d17411e7..9d86cbdfd663 100644
--- a/sys/conf/options
+++ b/sys/conf/options
@@ -95,6 +95,7 @@ _COMPAT_LINUX32	opt_compat.h	# XXX: make sure opt_compat.h exists
 COMPILING_LINT	opt_global.h
 CY_PCI_FASTINTR
 DEADLKRES	opt_watchdog.h
+EXPERIMENTAL	opt_global.h
 EXT_RESOURCES	opt_global.h
 DIRECTIO
 FILEMON		opt_dontuse.h
diff --git a/tools/build/options/WITH_EXPERIMENTAL b/tools/build/options/WITH_EXPERIMENTAL
new file mode 100644
index 000000000000..677edb6a081a
--- /dev/null
+++ b/tools/build/options/WITH_EXPERIMENTAL
@@ -0,0 +1,2 @@
+.\" $FreeBSD$
+Set to include experimental features in the build.