diff --git a/usr.bin/xlint/Makefile.inc b/usr.bin/xlint/Makefile.inc
index 3a49733b3a39..d244851539b8 100644
--- a/usr.bin/xlint/Makefile.inc
+++ b/usr.bin/xlint/Makefile.inc
@@ -1,4 +1,4 @@
-#	$NetBSD: Makefile.inc,v 1.18 2022/02/07 21:57:47 rillig Exp $
+#	$NetBSD: Makefile.inc,v 1.19 2022/02/26 18:35:01 rillig Exp $
 
 .include <bsd.own.mk>
 
@@ -16,6 +16,7 @@ ARCHSUBDIR=	${MACHINE_CPU}
 
 CPPFLAGS+=	-I${.CURDIR}/../arch/${ARCHSUBDIR}
 CPPFLAGS+=	-I${.CURDIR}/../common
+CPPFLAGS+=	-DBLKDEBUG
 
 CLEANFILES+=	*.gcno *.gcda *.gcov