diff -r dde85a5d47fc -r 67373614e125 web/request.py
--- a/web/request.py	Fri Feb 19 12:11:31 2016 +0100
+++ b/web/request.py	Mon Feb 29 17:07:56 2016 +0100
@@ -884,9 +884,15 @@
             self.session.data.pop(self.pageid, None)
         else:
             try:
-                del self.session.data[self.pageid][key]
+                page_data = self.session.data[self.pageid]
+                del page_data[key]
             except KeyError:
                 pass
+            else:
+                # make sure we write the session data value in the
+                # self.session.data dict-like object so any session
+                # handler can "detect" and manage the persistency
+                self.session.data[self.pageid] = page_data
 
     # user-agent detection ####################################################