diff --git a/tmt/result.py b/tmt/result.py
index 39bae5f8ce..c807f5e817 100644
--- a/tmt/result.py
+++ b/tmt/result.py
@@ -205,7 +205,7 @@ class Result(BaseResult):
             CheckResult.from_serialized(check) for check in serialized]
         )
     data_path: Optional[Path] = field(
-        default=None,
+        default=cast(Optional[Path], None),
         serialize=lambda path: None if path is None else str(path),
         unserialize=lambda value: None if value is None else Path(value)
         )
diff --git a/tmt/utils/__init__.py b/tmt/utils/__init__.py
index 942039e09f..919b01dc40 100644
--- a/tmt/utils/__init__.py
+++ b/tmt/utils/__init__.py
@@ -5522,7 +5522,8 @@ def dataclass_normalize_field(
     value = raw_value
 
     if dataclasses.is_dataclass(container):
-        _, _, _, _, metadata = container_field(type(container), keyname)
+        _, _, _, _, metadata = container_field(
+            type(container) if not isinstance(container, type) else container, keyname)
 
         if metadata.normalize_callback:
             value = metadata.normalize_callback(key_address, raw_value, logger)