diff --git a/gluon/tools.py b/gluon/tools.py
index 4620a366..48165799 100644
--- a/gluon/tools.py
+++ b/gluon/tools.py
@@ -6234,7 +6234,7 @@ class Expose(object):
                          and file creation under `base`.
 
         """
-        current.session.forget()
+        current.session and current.session.forget()
         self.follow_symlink_out = follow_symlink_out
         self.base = self.normalize_path(
             base or os.path.join(current.request.folder, 'static'))