diff --git a/arch/um/Makefile b/arch/um/Makefile
index c8016a98483b..5d5ed726faa0 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -64,9 +64,14 @@ CFLAGS += $(CFLAGS-y) -D__arch_um__ -DSUBARCH=\"$(SUBARCH)\"	\
 
 AFLAGS += $(ARCH_INCLUDE)
 
-USER_CFLAGS := $(patsubst -I%,,$(CFLAGS))
-USER_CFLAGS := $(patsubst -D__KERNEL__,,$(USER_CFLAGS)) $(ARCH_INCLUDE) \
-	$(MODE_INCLUDE) -D_FILE_OFFSET_BITS=64
+USER_CFLAGS = $(patsubst $(KERNEL_DEFINES),,$(patsubst -D__KERNEL__,,\
+	$(patsubst -I%,,$(CFLAGS)))) $(ARCH_INCLUDE) $(MODE_INCLUDE) \
+	-D_FILE_OFFSET_BITS=64
+
+include $(srctree)/$(ARCH_DIR)/Makefile-$(SUBARCH)
+
+#This will adjust *FLAGS accordingly to the platform.
+include $(srctree)/$(ARCH_DIR)/Makefile-os-$(OS)
 
 # -Derrno=kernel_errno - This turns all kernel references to errno into
 # kernel_errno to separate them from the libc errno.  This allows -fno-common
@@ -74,15 +79,11 @@ USER_CFLAGS := $(patsubst -D__KERNEL__,,$(USER_CFLAGS)) $(ARCH_INCLUDE) \
 # errnos.
 # These apply to kernelspace only.
 
-CFLAGS += -Derrno=kernel_errno -Dsigprocmask=kernel_sigprocmask \
-	-Dmktime=kernel_mktime
+KERNEL_DEFINES = -Derrno=kernel_errno -Dsigprocmask=kernel_sigprocmask \
+	-Dmktime=kernel_mktime $(ARCH_KERNEL_DEFINES)
+CFLAGS += $(KERNEL_DEFINES)
 CFLAGS += $(call cc-option,-fno-unit-at-a-time,)
 
-include $(srctree)/$(ARCH_DIR)/Makefile-$(SUBARCH)
-
-#This will adjust *FLAGS accordingly to the platform.
-include $(srctree)/$(ARCH_DIR)/Makefile-os-$(OS)
-
 # These are needed for clean and mrproper, since in that case .config is not
 # included; the values here are meaningless
 
diff --git a/arch/um/Makefile-i386 b/arch/um/Makefile-i386
index b65ca115ef77..c9f1c5b24c9a 100644
--- a/arch/um/Makefile-i386
+++ b/arch/um/Makefile-i386
@@ -16,7 +16,6 @@ OBJCOPYFLAGS  		:= -O binary -R .note -R .comment -S
 ifeq ("$(origin SUBARCH)", "command line")
 ifneq ("$(shell uname -m | sed -e s/i.86/i386/)", "$(SUBARCH)")
 CFLAGS			+= $(call cc-option,-m32)
-USER_CFLAGS		+= $(call cc-option,-m32)
 AFLAGS			+= $(call cc-option,-m32)
 LINK-y			+= $(call cc-option,-m32)
 UML_OBJCOPYFLAGS	+= -F $(ELF_FORMAT)
@@ -25,7 +24,7 @@ export LDFLAGS HOSTCFLAGS HOSTLDFLAGS UML_OBJCOPYFLAGS
 endif
 endif
 
-CFLAGS += -U__$(SUBARCH)__ -U$(SUBARCH)
+ARCH_KERNEL_DEFINES += -U__$(SUBARCH)__ -U$(SUBARCH)
 
 # First of all, tune CFLAGS for the specific CPU. This actually sets cflags-y.
 include $(srctree)/arch/i386/Makefile.cpu
@@ -38,4 +37,3 @@ cflags-y += $(call cc-option,-mpreferred-stack-boundary=2)
 cflags-y += -ffreestanding
 
 CFLAGS += $(cflags-y)
-USER_CFLAGS += $(cflags-y)
diff --git a/arch/um/Makefile-x86_64 b/arch/um/Makefile-x86_64
index d278682dd799..69ecea63fdae 100644
--- a/arch/um/Makefile-x86_64
+++ b/arch/um/Makefile-x86_64
@@ -8,8 +8,8 @@ _extra_flags_ = -fno-builtin -m64
 
 #We #undef __x86_64__ for kernelspace, not for userspace where
 #it's needed for headers to work!
-CFLAGS += -U__$(SUBARCH)__ $(_extra_flags_)
-USER_CFLAGS += $(_extra_flags_)
+ARCH_KERNEL_DEFINES = -U__$(SUBARCH)__
+CFLAGS += $(_extra_flags_)
 
 CHECKFLAGS  += -m64
 AFLAGS += -m64