diff --git a/arch/um/Makefile b/arch/um/Makefile
index 82c2ac4..768a5d1 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -70,9 +70,12 @@
 # in KBUILD_CFLAGS.  Otherwise, it would cause ld to complain about the two different
 # errnos.
 # These apply to kernelspace only.
+#
+# strip leading and trailing whitespace to make the USER_CFLAGS removal of these
+# defines more robust
 
-KERNEL_DEFINES = -Derrno=kernel_errno -Dsigprocmask=kernel_sigprocmask \
-	-Dmktime=kernel_mktime $(ARCH_KERNEL_DEFINES)
+KERNEL_DEFINES = $(strip -Derrno=kernel_errno -Dsigprocmask=kernel_sigprocmask \
+			 -Dmktime=kernel_mktime $(ARCH_KERNEL_DEFINES))
 KBUILD_CFLAGS += $(KERNEL_DEFINES)
 KBUILD_CFLAGS += $(call cc-option,-fno-unit-at-a-time,)