diff --git a/client.mk b/client.mk
index 50ab90deec3ba35bb1de68e8250984cdd9c776d9..cef82e779b4d9238138e60299392fec9cbdac5cd 100644
--- a/client.mk
+++ b/client.mk
@@ -192,6 +192,9 @@ ifdef WANT_MOZCONFIG_MK
 MOZCONFIG_MK_LINES := $(filter export||% UPLOAD_EXTRA_FILES% %UPLOAD_EXTRA_FILES%,$(MOZCONFIG_OUT_LINES))
 $(OBJDIR)/.mozconfig.mk: $(TOPSRCDIR)/client.mk $(FOUND_MOZCONFIG) $(call mkdir_deps,$(OBJDIR)) $(OBJDIR)/CLOBBER
 	$(if $(MOZCONFIG_MK_LINES),( $(foreach line,$(MOZCONFIG_MK_LINES), echo '$(subst ||, ,$(line))';) )) > $@
+ifdef MOZ_CURRENT_PROJECT
+	echo export MOZ_CURRENT_PROJECT=$(MOZ_CURRENT_PROJECT) >> $@
+endif
 
 # Include that makefile so that it is created. This should not actually change
 # the environment since MOZCONFIG_CONTENT, which MOZCONFIG_OUT_LINES derives
diff --git a/python/mozbuild/mozbuild/test/test_base.py b/python/mozbuild/mozbuild/test/test_base.py
index 950b3f199d7b47a0d15eba9636047866df515a06..ffcc26c2dd9a311e0d120ea1d931522034da7b1f 100644
--- a/python/mozbuild/mozbuild/test/test_base.py
+++ b/python/mozbuild/mozbuild/test/test_base.py
@@ -41,6 +41,7 @@ class TestMozbuildObject(unittest.TestCase):
         self._old_env = dict(os.environ)
         os.environ.pop('MOZCONFIG', None)
         os.environ.pop('MOZ_OBJDIR', None)
+        os.environ.pop('MOZ_CURRENT_PROJECT', None)
 
     def tearDown(self):
         os.chdir(self._old_cwd)