diff --git a/cache_manager/_cache.py b/cache_manager/_cache.py
index 0309501..b8ead11 100644
--- a/cache_manager/_cache.py
+++ b/cache_manager/_cache.py
@@ -376,15 +376,17 @@ def update(
 
             _log(f'Updating attributes in attr_{actual_typ}')
 
-            main = ', '.join(
+            values = ', '.join(
                 f'{k} = {self._quotes(v, main_fields[k])}'
-                for k, v in update.items() if k not in main_fields and
+                for k, v in update.items()
+                if (k not in main_fields and
+                    str(type(v)) == actual_typ)
             )
             ids = [it.id for it in items()]
             _log(f'Updating {len(ids)} items')
 
             where = f'WHERE id IN ({", ".join(ids)})'
 
-            q = f'UPDATE main SET ({main}) {where}'
+            q = f'UPDATE main SET ({values}) {where}'
 
             self._execute(q)
diff --git a/cache_manager/_item.py b/cache_manager/_item.py
index 46b30ad..40e1559 100644
--- a/cache_manager/_item.py
+++ b/cache_manager/_item.py
@@ -14,7 +14,7 @@ class CacheItem:
     Cache item class, stores a single cache item information.
     """
 
-    def __init__(# TODO:add filename
+    def __init__(
             self,
             key,
             version: int = 1,