diff --git a/sys/boot/arm/uboot/Makefile b/sys/boot/arm/uboot/Makefile
index 743f1897d05c..c69d8aaabb69 100644
--- a/sys/boot/arm/uboot/Makefile
+++ b/sys/boot/arm/uboot/Makefile
@@ -76,7 +76,7 @@ LIBUBOOT_FDT=	${.OBJDIR}/../../uboot/fdt/libuboot_fdt.a
 LIBFDT=		${.OBJDIR}/../../fdt/libfdt.a
 .endif
 
-.if !defined(NO_FORTH)
+.if ${MK_FORTH} != "no"
 # Enable BootForth
 BOOT_FORTH=	yes
 CFLAGS+=	-DBOOT_FORTH -I${.CURDIR}/../../ficl -I${.CURDIR}/../../ficl/arm
diff --git a/sys/boot/powerpc/uboot/Makefile b/sys/boot/powerpc/uboot/Makefile
index a5a06a9d84fb..681249aca78d 100644
--- a/sys/boot/powerpc/uboot/Makefile
+++ b/sys/boot/powerpc/uboot/Makefile
@@ -66,7 +66,7 @@ LIBUBOOT_FDT=	${.OBJDIR}/../../uboot/fdt/libuboot_fdt.a
 LIBFDT=		${.OBJDIR}/../../fdt/libfdt.a
 .endif
 
-.if !defined(NO_FORTH)
+.if ${MK_FORTH} != "no"
 # Enable BootForth
 BOOT_FORTH=	yes
 CFLAGS+=	-DBOOT_FORTH -I${.CURDIR}/../../ficl -I${.CURDIR}/../../ficl/powerpc