diff --git a/tests/test_filters/test_callback_data.py b/tests/test_filters/test_callback_data.py
index 7df6b433..506da4c3 100644
--- a/tests/test_filters/test_callback_data.py
+++ b/tests/test_filters/test_callback_data.py
@@ -149,7 +149,7 @@ class TestCallbackData:
         assert MyCallback3.unpack("test3:spam:42") == MyCallback3(foo="spam", bar=42)
 
         class MyCallback4(CallbackData, prefix="test4"):
-            foo: Optional[str] = ''
+            foo: Optional[str] = ""
             bar: Optional[str] = None
 
         assert MyCallback4.unpack("test4::") == MyCallback4(foo='', bar=None)