diff --git a/pycardano/address.py b/pycardano/address.py
index ba7a6dd7..61547edc 100644
--- a/pycardano/address.py
+++ b/pycardano/address.py
@@ -416,6 +416,7 @@ def save(
         path: str,
         key_type: Optional[str] = None,
         description: Optional[str] = None,
+        **kwargs,
     ):
         """
         Save the Address object to a file.
@@ -427,6 +428,7 @@ def save(
             path (str): The file path to save the object to.
             key_type (str, optional): Not used in this context, but can be included for consistency.
             description (str, optional): Not used in this context, but can be included for consistency.
+            **kwargs: Additional keyword arguments (not used here).
 
         Raises:
             IOError: If the file already exists and is not empty.
diff --git a/pycardano/key.py b/pycardano/key.py
index e8bce690..d2d728d8 100644
--- a/pycardano/key.py
+++ b/pycardano/key.py
@@ -73,7 +73,7 @@ def to_primitive(self) -> bytes:
     def from_primitive(cls: Type["Key"], value: bytes) -> Key:
         return cls(value)
 
-    def to_json(self, **kwargs) -> str:
+    def to_json(self, **kwargs) -> str:  # type: ignore
         """Serialize the key to JSON.
 
         The json output has three fields: "type", "description", and "cborHex".
@@ -90,7 +90,7 @@ def to_json(self, **kwargs) -> str:
         )
 
     @classmethod
-    def from_json(cls: Type[Key], data: str, validate_type=False) -> Key:
+    def from_json(cls: Type[Key], data: str, validate_type=False) -> Key:  # type: ignore
         """Restore a key from a JSON string.
 
         Args:
diff --git a/pycardano/plutus.py b/pycardano/plutus.py
index 435c8f4f..83c66705 100644
--- a/pycardano/plutus.py
+++ b/pycardano/plutus.py
@@ -652,7 +652,7 @@ def _dfs(obj):
 
         return _dfs(self)
 
-    def to_json(self, **kwargs) -> str:
+    def to_json(self, **kwargs) -> str:  # type: ignore
         """Convert to a json string
 
         Args:
@@ -847,7 +847,7 @@ def _dfs(obj):
 
         return _dfs(RawPlutusData.to_primitive(self))
 
-    def to_json(self, **kwargs) -> str:
+    def to_json(self, **kwargs) -> str:  # type: ignore
         """Convert to a json string
 
         Args:
diff --git a/pycardano/serialization.py b/pycardano/serialization.py
index 63e13586..22f51a92 100644
--- a/pycardano/serialization.py
+++ b/pycardano/serialization.py
@@ -561,29 +561,35 @@ def json_description(self) -> str:
         """
         return self.__class__.__doc__ or "Generated with PyCardano"
 
-    def to_json(self, **kwargs) -> str:
+    def to_json(
+        self,
+        key_type: Optional[str] = None,
+        description: Optional[str] = None,
+        **kwargs,
+    ) -> str:
         """
         Convert the CBORSerializable object to a JSON string containing type, description, and CBOR hex.
 
         This method returns a JSON representation of the object, including its type, description, and CBOR hex encoding.
 
         Args:
-            **kwargs: Additional keyword arguments that can include:
-                - key_type (str): The type to use in the JSON output. Defaults to the class name.
-                - description (str): The description to use in the JSON output. Defaults to the class docstring.
+            key_type (str): The type to use in the JSON output. Defaults to the class name.
+            description (str): The description to use in the JSON output. Defaults to the class docstring.
+            **kwargs: Extra key word arguments to be passed to `json.dumps()`
 
         Returns:
             str: The JSON string representation of the object.
         """
-        key_type = kwargs.pop("key_type", self.json_type)
-        description = kwargs.pop("description", self.json_description)
+        if "indent" not in kwargs:
+            kwargs["indent"] = 2
+
         return json.dumps(
             {
-                "type": key_type,
-                "description": description,
+                "type": key_type or self.json_type,
+                "description": description or self.json_description,
                 "cborHex": self.to_cbor_hex(),
             },
-            indent=2,
+            **kwargs,
         )
 
     @classmethod
@@ -616,6 +622,7 @@ def save(
         path: str,
         key_type: Optional[str] = None,
         description: Optional[str] = None,
+        **kwargs,
     ):
         """
         Save the CBORSerializable object to a file in JSON format.
@@ -625,8 +632,9 @@ def save(
 
         Args:
             path (str): The file path to save the object to.
-            key_type (str, optional): The type to use in the JSON output.
-            description (str, optional): The description to use in the JSON output.
+            key_type (str, optional): The type to use in the JSON output. Defaults to the class name.
+            description (str, optional): The description to use in the JSON output. Defaults to the class docstring.
+            **kwargs: Extra key word arguments to be passed to `json.dumps()`
 
         Raises:
             IOError: If the file already exists and is not empty.
@@ -634,7 +642,7 @@ def save(
         if os.path.isfile(path) and os.stat(path).st_size > 0:
             raise IOError(f"File {path} already exists!")
         with open(path, "w") as f:
-            f.write(self.to_json(key_type=key_type, description=description))
+            f.write(self.to_json(key_type=key_type, description=description, **kwargs))
 
     @classmethod
     def load(cls, path: str):
diff --git a/pycardano/transaction.py b/pycardano/transaction.py
index d9f5515f..a193baf7 100644
--- a/pycardano/transaction.py
+++ b/pycardano/transaction.py
@@ -698,7 +698,7 @@ class Transaction(ArrayCBORSerializable):
     def json_type(self) -> str:
         return (
             "Unwitnessed Tx ConwayEra"
-            if self.transaction_witness_set.is_empty()
+            if self.transaction_witness_set.vkey_witnesses is None
             else "Signed Tx ConwayEra"
         )