diff --git a/Config.mk b/Config.mk
index 4a5ebedb35..9b097c9831 100644
--- a/Config.mk
+++ b/Config.mk
@@ -132,7 +132,7 @@ $(eval $(check-y))
 # as-insn: Check whether assembler supports an instruction.
 # Usage: cflags-y += $(call as-insn "insn",option-yes,option-no)
 as-insn = $(if $(shell echo 'void _(void) { asm volatile ( $(2) ); }' \
-                       | $(1) -c -x c -o /dev/null - 2>&1),$(4),$(3))
+                       | $(1) $(AFLAGS) -c -x c -o /dev/null - 2>&1),$(4),$(3))
 
 # as-insn-check: Add an option to compilation flags, but only if insn is
 #                supported by assembler.
diff --git a/xen/Rules.mk b/xen/Rules.mk
index 7183d6938c..961d533da2 100644
--- a/xen/Rules.mk
+++ b/xen/Rules.mk
@@ -38,8 +38,6 @@ override TARGET_ARCH     := $(shell echo $(XEN_TARGET_ARCH) | \
 
 TARGET := $(BASEDIR)/xen
 
-include $(BASEDIR)/arch/$(TARGET_ARCH)/Rules.mk
-
 # Note that link order matters!
 ALL_OBJS-y               += $(BASEDIR)/common/built_in.o
 ALL_OBJS-y               += $(BASEDIR)/drivers/built_in.o
@@ -92,6 +90,8 @@ LDFLAGS += $(LDFLAGS_DIRECT)
 
 LDFLAGS += $(LDFLAGS-y)
 
+include $(BASEDIR)/arch/$(TARGET_ARCH)/Rules.mk
+
 include Makefile
 
 DEPS = .*.d