--- a/server/utils.py	Thu Feb 14 15:38:25 2013 +0100
+++ b/server/utils.py	Thu Feb 14 16:01:24 2013 +0100
@@ -93,7 +93,7 @@
 
 def cleanup_solutions(rqlst, solutions):
     for sol in solutions:
-        for vname in sol.keys():
+        for vname in list(sol):
             if not (vname in rqlst.defined_vars or vname in rqlst.aliases):
                 del sol[vname]