diff --git a/distutils/command/install.py b/distutils/command/install.py
index 4f944725..fceb36aa 100644
--- a/distutils/command/install.py
+++ b/distutils/command/install.py
@@ -395,7 +395,7 @@ def finalize_options(self):
                             'platlibdir': getattr(sys, 'platlibdir', 'lib'),
                             'implementation_lower': _get_implementation().lower(),
                             'implementation': _get_implementation(),
-                            'platsubdir': sysconfig.get_config_var('platsubdir'),
+                            'platsubdir': sysconfig.get_config_var('platsubdir') or '',
                            }
 
         if HAS_USER_SITE: