Index: pylib/gyp/input.py
===================================================================
--- pylib/gyp/input.py	(revision 1556)
+++ pylib/gyp/input.py	(working copy)
@@ -857,7 +857,8 @@
           # that don't load quickly, this can be faster than
           # <!(python modulename param eters). Do this in |build_file_dir|.
           oldwd = os.getcwd()  # Python doesn't like os.open('.'): no fchdir.
-          os.chdir(build_file_dir)
+          if not build_file_dir is None:
+            os.chdir(build_file_dir)
           try:
 
             parsed_contents = shlex.split(contents)