diff --git a/Makefile b/Makefile
index c3b54ad2f..a88062e54 100644
--- a/Makefile
+++ b/Makefile
@@ -12,12 +12,11 @@ noconfig_targets := menuconfig config oldconfig randconfig \
 	defconfig allyesconfig allnoconfig clean distclean \
 	release tags
 
-ifndef TOPDIR
-TOPDIR=$(CURDIR)/
-endif
+# the toplevel sourcedir
 ifndef top_srcdir
 top_srcdir=$(CURDIR)
 endif
+# toplevel directory of the object-tree
 ifndef top_builddir
 top_builddir=$(CURDIR)
 endif
@@ -70,7 +69,6 @@ $(filter-out _all,$(MAKECMDGOALS)) _all: $(KBUILD_OUTPUT)/Rules.mak $(KBUILD_OUT
 	$(MAKE) -C $(KBUILD_OUTPUT) \
 	top_srcdir=$(CURDIR) \
 	top_builddir=$(KBUILD_OUTPUT) \
-	TOPDIR=$(KBUILD_OUTPUT) \
 	KBUILD_SRC=$(CURDIR) \
 	-f $(CURDIR)/Makefile $@
 
diff --git a/Rules.mak b/Rules.mak
index e186af00d..b18d09b96 100644
--- a/Rules.mak
+++ b/Rules.mak
@@ -84,7 +84,7 @@ CFLAGS=-I$(top_builddir)/include -I$(top_srcdir)/include -I$(srcdir)
 ARFLAGS=cru
 
 #--------------------------------------------------------
-export VERSION BUILDTIME TOPDIR HOSTCC HOSTCFLAGS CROSS CC AR AS LD NM STRIP CPP
+export VERSION BUILDTIME HOSTCC HOSTCFLAGS CROSS CC AR AS LD NM STRIP CPP
 ifeq ($(strip $(TARGET_ARCH)),)
 TARGET_ARCH:=$(shell $(CC) -dumpmachine | sed -e s'/-.*//' \
 		-e 's/i.86/i386/' \