diff --git a/jedi/api/environment.py b/jedi/api/environment.py
index 2bf6f68a..ea34d90b 100644
--- a/jedi/api/environment.py
+++ b/jedi/api/environment.py
@@ -190,8 +190,9 @@ def get_default_environment():
 
 
 def get_cached_default_environment():
+    var = os.environ.get('VIRTUAL_ENV')
     environment = _get_cached_default_environment()
-    if environment.path != os.environ.get('VIRTUAL_ENV'):
+    if var and var != environment.path:
         _get_cached_default_environment.clear_cache()
         return _get_cached_default_environment()
     return environment