diff --git a/build/subconfigure.py b/build/subconfigure.py
index e91c66aeb43e..0ee6b6235343 100644
--- a/build/subconfigure.py
+++ b/build/subconfigure.py
@@ -314,6 +314,7 @@ def run(objdir):
             command = [
                 sys.executable,
                 os.path.join(os.path.dirname(__file__), '..', 'configure.py'),
+                '--enable-project=js',
             ]
             data['env']['OLD_CONFIGURE'] = os.path.join(
                 os.path.dirname(configure), 'old-configure')
diff --git a/old-configure.in b/old-configure.in
index a65ca67d0d55..5a758386b753 100644
--- a/old-configure.in
+++ b/old-configure.in
@@ -7943,6 +7943,7 @@ export MOZILLA_CENTRAL_PATH=$_topsrcdir
 export STLPORT_CPPFLAGS
 export STLPORT_LIBS
 export JS_STANDALONE=no
+unset MOZ_BUILD_APP
 export DIST
 export MOZ_LINKER
 export ZLIB_IN_MOZGLUE