diff --git a/share/mk/bsd.mkopt.mk b/share/mk/bsd.mkopt.mk
--- a/share/mk/bsd.mkopt.mk
+++ b/share/mk/bsd.mkopt.mk
@@ -19,9 +19,10 @@
 # If both WITH_FOO and WITHOUT_FOO are defined, WITHOUT_FOO wins and
 # MK_FOO is set to "no" regardless of which list it was in.
 #
-# All of __DEFAULT_YES_OPTIONS, __DEFAULT_NO_OPTIONS and
-# __DEFAULT_DEPENDENT_OPTIONS are undef'd after all this processing,
-# allowing this file to be included multiple times with different lists.
+# All of __REQUIRED_OPTIONS, __DEFAULT_DEPENDENT_OPTIONS,
+# __DEFAULT_YES_OPTIONS, and __DEFAULT_NO_OPTIONS are undef'd after
+# all this processing, allowing this file to be included multiple
+# times with different lists.
 #
 # Other parts of the build system will set BROKEN_OPTIONS to a list
 # of options that are broken on this platform. This will not be unset
@@ -72,6 +73,7 @@
 .endif
 MK_${var}:=	yes
 .endfor
+.undef __REQUIRED_OPTIONS
 
 #
 # MK_* options which default to "no".