diff --git a/arch/um/Makefile b/arch/um/Makefile
index c8016a9..5d5ed72 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -64,9 +64,14 @@
 
 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 @@
 # 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