Index: Lib/distutils/sysconfig.py
===================================================================
--- Lib/distutils/sysconfig.py	(revision 66981)
+++ Lib/distutils/sysconfig.py	(working copy)
@@ -521,6 +526,9 @@
         _config_vars['prefix'] = PREFIX
         _config_vars['exec_prefix'] = EXEC_PREFIX
 
+        if 'srcdir' not in _config_vars:
+            _config_vars['srcdir'] = project_base
+
         if sys.platform == 'darwin':
             kernel_version = os.uname()[2] # Kernel version (8.4.3)
             major_version = int(kernel_version.split('.')[0])