diff --git a/Makefile.inc1 b/Makefile.inc1
index 60956d58fd9b..d059d5dd9fea 100644
--- a/Makefile.inc1
+++ b/Makefile.inc1
@@ -3405,9 +3405,11 @@ check-old: check-old-files check-old-libs check-old-dirs .PHONY
 #
 # showconfig - show build configuration.
 #
+# ignore lower case knobs (not for use with WITH*)
+#
 showconfig: .PHONY
 	@(${MAKE} -n -f ${.CURDIR}/sys/conf/kern.opts.mk -V dummy -dg1 UPDATE_DEPENDFILE=no NO_OBJ=yes MACHINE=${TARGET} MACHINE_ARCH=${TARGET_ARCH}; \
-	  ${MAKE} -n -f ${.CURDIR}/share/mk/src.opts.mk -V dummy -dg1 UPDATE_DEPENDFILE=no NO_OBJ=yes) 2>&1 | grep ^MK_ | sort -u
+	  ${MAKE} -n -f ${.CURDIR}/share/mk/src.opts.mk -V dummy -dg1 UPDATE_DEPENDFILE=no NO_OBJ=yes) 2>&1 | grep '^MK_[A-Z]' | sort -u
 
 .if !empty(KRNLOBJDIR) && !empty(KERNCONF)
 DTBOUTPUTPATH= ${KRNLOBJDIR}/${KERNCONF}/