diff --git a/lib/core/decorators.py b/lib/core/decorators.py
index 31ce7535a..ab8978c1a 100644
--- a/lib/core/decorators.py
+++ b/lib/core/decorators.py
@@ -13,7 +13,10 @@ def cachedmethod(f, cache={}):
     """
 
     def _(*args, **kwargs):
-        key = (f, tuple(args), str(kwargs))
+        try:
+            key = (f, tuple(args), frozenset(kwargs.items()))
+        except:
+            key = "".join(str(_) for _ in (f, args, kwargs))
         if key not in cache:
             cache[key] = f(*args, **kwargs)
         return cache[key]