diff --git a/cache_manager/_cache.py b/cache_manager/_cache.py
index 6bb5e79..49a4524 100644
--- a/cache_manager/_cache.py
+++ b/cache_manager/_cache.py
@@ -15,6 +15,7 @@
 import datetime
 import functools as ft
 import collections
+from collections.abc import Mapping
 
 from pypath_common import _misc
 import platformdirs
@@ -1108,7 +1109,7 @@ def update(
                     (
                         0,
                         self._quotes(group)
-                            if isinstance(vals, dict)
+                            if isinstance(vals, Mapping)
                             else 'NULL',
                         k,
                         v
@@ -1116,7 +1117,7 @@ def update(
                     for group, vals in update.get('attrs', {}).items()
                     for k, v in (
                         vals
-                        if isinstance(vals, dict) else
+                        if isinstance(vals, Mapping) else
                         {group: vals}
                     ).items()
                     if (
diff --git a/cache_manager/_item.py b/cache_manager/_item.py
index 62c0f13..62e2230 100644
--- a/cache_manager/_item.py
+++ b/cache_manager/_item.py
@@ -283,6 +283,19 @@ def path(self) -> str:
 
         return os.path.join(d, self.cache_fname)
 
+    @property
+    def size(self) -> int | None:
+        """
+        Size of the file in bytes.
+
+        Returns:
+            Size of the file in bytes.
+        """
+
+        if os.path.exists(path := self.path):
+
+            return os.path.getsize(path)
+
 
     @property
     def rstatus(self) -> int:
diff --git a/tests/test_item.py b/tests/test_item.py
new file mode 100644
index 0000000..2fad4f1
--- /dev/null
+++ b/tests/test_item.py
@@ -0,0 +1,15 @@
+import os
+
+import pytest
+
+def test_size(test_cache):
+    it = test_cache.create('test-file-size')
+    path = it.path
+
+    assert it.size is None
+
+    with open(path, 'w') as fp:
+        fp.write('something')
+
+    assert os.path.exists(path)
+    assert it.size > 8