diff --git a/setup.py b/setup.py
index b79a84d1ed8e5e7a4c27836f2713378986b2816a..2daa9a369560d620e78867e8eb820e94ae5426ea 100755
--- a/setup.py
+++ b/setup.py
@@ -15,12 +15,13 @@
 
 import glob
 import os
+import sys
 # pylint: disable=E0611
 
 from setuptools import setup, find_packages
 
 
-VIRTUAL_ENV = 'VIRTUAL_ENV' in os.environ
+VIRTUAL_ENV = hasattr(sys, 'real_prefix')
 
 
 def get_dir(system_path=None, virtual_path=None):