diff --git a/boot/syslinux/syslinux.mk b/boot/syslinux/syslinux.mk
index 2df415fcfd..cc52c49aee 100644
--- a/boot/syslinux/syslinux.mk
+++ b/boot/syslinux/syslinux.mk
@@ -58,6 +58,8 @@ SYSLINUX_POST_PATCH_HOOKS += SYSLINUX_CLEANUP
 # be used.
 define SYSLINUX_BUILD_CMDS
 	$(TARGET_MAKE_ENV) $(MAKE1) \
+		ASCIIDOC_OK=-1 \
+		A2X_XML_OK=-1 \
 		CC="$(TARGET_CC)" \
 		LD="$(TARGET_LD)" \
 		OBJCOPY="$(TARGET_OBJCOPY)" \