diff --git a/Doc/conf.py b/Doc/conf.py
index c4ae16a2054..aaee983984b 100644
--- a/Doc/conf.py
+++ b/Doc/conf.py
@@ -38,7 +38,8 @@
 needs_sphinx = '1.2'
 
 # Ignore any .rst files in the venv/ directory.
-exclude_patterns = ['venv/*', 'README.rst']
+venvdir = os.getenv('VENVDIR', 'venv')
+exclude_patterns = [venvdir+'/*', 'README.rst']
 
 
 # Options for HTML output