diff --git a/make/linux-rpm.mk b/make/linux-rpm.mk
index c88cebbf..2b49267a 100644
--- a/make/linux-rpm.mk
+++ b/make/linux-rpm.mk
@@ -92,7 +92,7 @@ config-$(KERNEL_VERSION):
 	cvs commit
 
 toplevel-makefile: unpack.done
-	sed "s/^ *EXTRAVERSION *=/EXTRAVERSION = -$(KERNEL_RELEASE)/" linux-$(KERNEL_VERSION)/Makefile >$@
+	sed "/^ *EXTRAVERSION *=/ !d; s/ *$$/-$(KERNEL_RELEASE)/" linux-$(KERNEL_VERSION)/Makefile >$@
 
 linux-$(KERNEL_VERSION)/Makefile: toplevel-makefile
 	cp $< $@