diff --git a/config/config.mk b/config/config.mk
index ede5020d8d5..948a71af209 100644
--- a/config/config.mk
+++ b/config/config.mk
@@ -94,7 +94,7 @@ check-variable = $(if $(filter-out 0 1,$(words $($(x))z)),$(error Spaces are not
 $(foreach x,$(CHECK_VARS),$(check-variable))
 
 ifndef INCLUDED_FUNCTIONS_MK
-include $(topsrcdir)/config/makefiles/functions.mk
+include $(MOZILLA_DIR)/config/makefiles/functions.mk
 endif
 
 RM = rm -f
@@ -138,7 +138,7 @@ else
 endif
 
 CONFIG_TOOLS	= $(MOZ_BUILD_ROOT)/config
-AUTOCONF_TOOLS	= $(topsrcdir)/build/autoconf
+AUTOCONF_TOOLS	= $(MOZILLA_DIR)/build/autoconf
 
 #
 # Strip off the excessively long version numbers on these platforms,
@@ -337,7 +337,7 @@ OS_INCLUDES := \
   $(NULL)
 endif
 
-include $(topsrcdir)/config/static-checking-config.mk
+include $(MOZILLA_DIR)/config/static-checking-config.mk
 
 CFLAGS		= $(OS_CPPFLAGS) $(OS_CFLAGS)
 CXXFLAGS	= $(OS_CPPFLAGS) $(OS_CXXFLAGS)
@@ -528,7 +528,7 @@ endif
 PWD := $(CURDIR)
 endif
 
-NSINSTALL_PY := $(PYTHON) $(abspath $(topsrcdir)/config/nsinstall.py)
+NSINSTALL_PY := $(PYTHON) $(abspath $(MOZILLA_DIR)/config/nsinstall.py)
 # For Pymake, wherever we use nsinstall.py we're also going to try to make it
 # a native command where possible. Since native commands can't be used outside
 # of single-line commands, we continue to provide INSTALL for general use.
@@ -629,13 +629,13 @@ ifdef MOZ_DEBUG
 JAVAC_FLAGS += -g
 endif
 
-CREATE_PRECOMPLETE_CMD = $(PYTHON) $(abspath $(topsrcdir)/config/createprecomplete.py)
+CREATE_PRECOMPLETE_CMD = $(PYTHON) $(abspath $(MOZILLA_DIR)/config/createprecomplete.py)
 
 # MDDEPDIR is the subdirectory where dependency files are stored
 MDDEPDIR := .deps
 
-EXPAND_LIBS_EXEC = $(PYTHON) $(topsrcdir)/config/expandlibs_exec.py
-EXPAND_LIBS_GEN = $(PYTHON) $(topsrcdir)/config/expandlibs_gen.py
+EXPAND_LIBS_EXEC = $(PYTHON) $(MOZILLA_DIR)/config/expandlibs_exec.py
+EXPAND_LIBS_GEN = $(PYTHON) $(MOZILLA_DIR)/config/expandlibs_gen.py
 EXPAND_AR = $(EXPAND_LIBS_EXEC) --extract -- $(AR)
 EXPAND_CC = $(EXPAND_LIBS_EXEC) --uselist -- $(CC)
 EXPAND_CCC = $(EXPAND_LIBS_EXEC) --uselist -- $(CCC)
@@ -689,7 +689,7 @@ endif
 endif
 endif
 
-PLY_INCLUDE = -I$(topsrcdir)/other-licenses/ply
+PLY_INCLUDE = -I$(MOZILLA_DIR)/other-licenses/ply
 
 export CL_INCLUDES_PREFIX
 # Make sure that the build system can handle non-ASCII characters
diff --git a/config/makefiles/makeutils.mk b/config/makefiles/makeutils.mk
index 0ae1044643c..07961c797c0 100644
--- a/config/makefiles/makeutils.mk
+++ b/config/makefiles/makeutils.mk
@@ -107,7 +107,11 @@ endif #}
 ###########################################################################
 ## Common makefile library loader
 ###########################################################################
-topORerr =$(if $(topsrcdir),$(topsrcdir),$(error topsrcdir is not defined))
+ifdef MOZILLA_DIR
+topORerr = $(MOZILLA_DIR)
+else
+topORerr = $(if $(topsrcdir),$(topsrcdir),$(error topsrcdir is not defined))
+endif
 
 ifdef USE_AUTOTARGETS_MK # mkdir_deps
   include $(topORerr)/config/makefiles/autotargets.mk
diff --git a/config/rules.mk b/config/rules.mk
index 5f7b66c8129..7c5bbb4d4bc 100644
--- a/config/rules.mk
+++ b/config/rules.mk
@@ -25,11 +25,11 @@ include $(topsrcdir)/config/config.mk
 endif
 
 ifndef INCLUDED_VERSION_MK
-include $(topsrcdir)/config/version.mk
+include $(MOZILLA_DIR)/config/version.mk
 endif
 
 USE_AUTOTARGETS_MK = 1
-include $(topsrcdir)/config/makefiles/makeutils.mk
+include $(MOZILLA_DIR)/config/makefiles/makeutils.mk
 
 ifdef REBUILD_CHECK
 REPORT_BUILD = $(info $(shell $(PYTHON) $(MOZILLA_DIR)/config/rebuild_check.py $@ $^))
@@ -87,12 +87,12 @@ INSTALL_TARGETS += CPP_UNIT_TESTS
 endif
 
 run-cppunittests::
-	@$(PYTHON) $(topsrcdir)/testing/runcppunittests.py --xre-path=$(DIST)/bin --symbols-path=$(DIST)/crashreporter-symbols $(CPP_UNIT_TESTS)
+	@$(PYTHON) $(MOZILLA_DIR)/testing/runcppunittests.py --xre-path=$(DIST)/bin --symbols-path=$(DIST)/crashreporter-symbols $(CPP_UNIT_TESTS)
 
 cppunittests-remote: DM_TRANS?=adb
 cppunittests-remote:
 	@if [ '${TEST_DEVICE}' != '' -o '$(DM_TRANS)' = 'adb' ]; then \
-		$(PYTHON) -u $(topsrcdir)/testing/remotecppunittests.py \
+		$(PYTHON) -u $(MOZILLA_DIR)/testing/remotecppunittests.py \
 			--xre-path=$(DEPTH)/dist/bin \
 			--localLib=$(DEPTH)/dist/$(MOZ_APP_NAME) \
 			--dm_trans=$(DM_TRANS) \
@@ -220,7 +220,7 @@ endif # WINNT
 
 ifeq ($(SOLARIS_SUNPRO_CXX),1)
 ifeq (86,$(findstring 86,$(OS_TEST)))
-OS_LDFLAGS += -M $(topsrcdir)/config/solaris_ia32.map
+OS_LDFLAGS += -M $(MOZILLA_DIR)/config/solaris_ia32.map
 endif # x86
 endif # Solaris Sun Studio C++
 
@@ -557,7 +557,7 @@ STATIC_LIB_DEP = $(if $(wildcard $(1).$(LIBS_DESC_SUFFIX)),$(1).$(LIBS_DESC_SUFF
 STATIC_LIBS_DEPS := $(foreach l,$(STATIC_LIBS),$(call STATIC_LIB_DEP,$(l)))
 
 # Dependencies which, if modified, should cause everything to rebuild
-GLOBAL_DEPS += Makefile $(addprefix $(DEPTH)/config/,$(INCLUDED_AUTOCONF_MK)) $(topsrcdir)/config/config.mk
+GLOBAL_DEPS += Makefile $(addprefix $(DEPTH)/config/,$(INCLUDED_AUTOCONF_MK)) $(MOZILLA_DIR)/config/config.mk
 
 ##############################################
 ifdef COMPILE_ENVIRONMENT
@@ -569,7 +569,7 @@ host:: $(HOST_LIBRARY) $(HOST_PROGRAM) $(HOST_SIMPLE_PROGRAMS)
 
 target:: $(LIBRARY) $(SHARED_LIBRARY) $(PROGRAM) $(SIMPLE_PROGRAMS)
 
-include $(topsrcdir)/config/makefiles/target_binaries.mk
+include $(MOZILLA_DIR)/config/makefiles/target_binaries.mk
 endif
 
 ##############################################
@@ -594,11 +594,11 @@ endif
 ifneq (,$(SHARED_LIBRARY)$(PROGRAM))
 export::
 ifdef PROGRAM
-	$(PYTHON) $(topsrcdir)/build/win32/pgomerge.py \
+	$(PYTHON) $(MOZILLA_DIR)/build/win32/pgomerge.py \
 	  $(PROGRAM:$(BIN_SUFFIX)=) $(DIST)/bin
 endif
 ifdef SHARED_LIBRARY
-	$(PYTHON) $(topsrcdir)/build/win32/pgomerge.py \
+	$(PYTHON) $(MOZILLA_DIR)/build/win32/pgomerge.py \
 	  $(patsubst $(DLL_PREFIX)%$(DLL_SUFFIX),%,$(SHARED_LIBRARY)) $(DIST)/bin
 endif
 endif # SHARED_LIBRARY || PROGRAM
@@ -852,14 +852,14 @@ define MAKE_DEPS_AUTO_CC
 if test -d $(@D); then \
 	echo 'Building deps for $< using Sun Studio cc'; \
 	$(CC) $(COMPILE_CFLAGS) -xM  $< >$(_MDDEPFILE) ; \
-	$(PYTHON) $(topsrcdir)/build/unix/add_phony_targets.py $(_MDDEPFILE) ; \
+	$(PYTHON) $(MOZILLA_DIR)/build/unix/add_phony_targets.py $(_MDDEPFILE) ; \
 fi
 endef
 define MAKE_DEPS_AUTO_CXX
 if test -d $(@D); then \
 	echo 'Building deps for $< using Sun Studio CC'; \
 	$(CXX) $(COMPILE_CXXFLAGS) -xM $< >$(_MDDEPFILE) ; \
-	$(PYTHON) $(topsrcdir)/build/unix/add_phony_targets.py $(_MDDEPFILE) ; \
+	$(PYTHON) $(MOZILLA_DIR)/build/unix/add_phony_targets.py $(_MDDEPFILE) ; \
 fi
 endef
 endif # Sun Studio on Solaris
@@ -1097,7 +1097,7 @@ endif
 # Java rules
 ###############################################################################
 ifneq (,$(JAVAFILES)$(ANDROID_RESFILES)$(ANDROID_APKNAME)$(JAVA_JAR_TARGETS))
-  include $(topsrcdir)/config/makefiles/java-build.mk
+  include $(MOZILLA_DIR)/config/makefiles/java-build.mk
 endif
 
 ###############################################################################
@@ -1543,7 +1543,7 @@ endif
 
 # Pull in non-recursive targets if this is a partial tree build.
 ifndef TOPLEVEL_BUILD
-include $(topsrcdir)/config/makefiles/nonrecursive.mk
+include $(MOZILLA_DIR)/config/makefiles/nonrecursive.mk
 endif
 
 ################################################################################
@@ -1578,7 +1578,7 @@ TAGS: $(CSRCS) $(CPPSRCS) $(wildcard *.h)
 ifndef INCLUDED_DEBUGMAKE_MK #{
   ## Only parse when an echo* or show* target is requested
   ifneq (,$(call isTargetStem,echo,show))
-    include $(topsrcdir)/config/makefiles/debugmake.mk
+    include $(MOZILLA_DIR)/config/makefiles/debugmake.mk
   endif #}
 endif #}
 
@@ -1628,7 +1628,7 @@ $(PURGECACHES_FILES):
 #############################################################################
 # Derived targets and dependencies
 
-include $(topsrcdir)/config/makefiles/autotargets.mk
+include $(MOZILLA_DIR)/config/makefiles/autotargets.mk
 ifneq ($(NULL),$(AUTO_DEPS))
   default all libs tools export:: $(AUTO_DEPS)
 endif
diff --git a/config/version.mk b/config/version.mk
index 414a1ebb456..1b9f68afa95 100644
--- a/config/version.mk
+++ b/config/version.mk
@@ -15,7 +15,7 @@ ifeq ($(MOZ_WIDGET_TOOLKIT),windows)
 ifndef RESFILE
 RCFILE=./module.rc
 RESFILE=./module.res
-_RC_STRING = -QUIET 1 -DEPTH $(DEPTH) -TOPSRCDIR $(topsrcdir) -OBJDIR . -SRCDIR $(srcdir) -DISPNAME $(MOZ_APP_DISPLAYNAME) -APPVERSION $(MOZ_APP_VERSION)
+_RC_STRING = -QUIET 1 -DEPTH $(DEPTH) -TOPSRCDIR $(MOZILLA_DIR) -OBJDIR . -SRCDIR $(srcdir) -DISPNAME $(MOZ_APP_DISPLAYNAME) -APPVERSION $(MOZ_APP_VERSION)
 ifdef MOZILLA_OFFICIAL
 _RC_STRING += -OFFICIAL 1
 endif
@@ -42,8 +42,8 @@ GARBAGE += $(RESFILE) $(RCFILE)
 #dummy target so $(RCFILE) doesn't become the default =P
 all::
 
-$(RCFILE): $(RCINCLUDE) $(topsrcdir)/config/version_win.pl
-	$(PERL) $(topsrcdir)/config/version_win.pl $(_RC_STRING)
+$(RCFILE): $(RCINCLUDE) $(MOZILLA_DIR)/config/version_win.pl
+	$(PERL) $(MOZILLA_DIR)/config/version_win.pl $(_RC_STRING)
 
 endif  # RESFILE
 endif  # Windows
diff --git a/toolkit/mozapps/installer/package-name.mk b/toolkit/mozapps/installer/package-name.mk
index a88061b90be..3c13c66da8d 100644
--- a/toolkit/mozapps/installer/package-name.mk
+++ b/toolkit/mozapps/installer/package-name.mk
@@ -139,7 +139,7 @@ endif
 
 ifndef INCLUDED_RCS_MK
   USE_RCS_MK := 1
-  include $(topsrcdir)/config/makefiles/makeutils.mk
+  include $(MOZILLA_DIR)/config/makefiles/makeutils.mk
 endif
 
 MOZ_SOURCE_STAMP = $(firstword $(shell hg -R $(MOZILLA_DIR) parent --template="{node|short}\n" 2>/dev/null))