diff --git a/scalecodec/types.py b/scalecodec/types.py
index 368286b..0290256 100644
--- a/scalecodec/types.py
+++ b/scalecodec/types.py
@@ -147,12 +147,18 @@ class Option(ScaleType):
     def process(self):
 
         option_byte = self.get_next_bytes(1)
-
-        if self.sub_type and option_byte != b'\x00':
+        if self.sub_type is None:
+            raise ValueError("Plain 'Option' without type parameter is not valid as a type")
+        if option_byte == b'\x01':
             self.value_object = self.process_type(self.sub_type)
             return self.value_object.value
+        elif option_byte == b'\x00':
+            return None
+        else:
+            raise InvalidScaleTypeValueException(
+                f"Invalid starting byte for 'Option': '0x{option_byte.hex()}'"
+            )
 
-        return None
 
     def process_encode(self, value):
 
diff --git a/test/test_type_encoding.py b/test/test_type_encoding.py
index dedd2ac..03dfc00 100644
--- a/test/test_type_encoding.py
+++ b/test/test_type_encoding.py
@@ -17,6 +17,7 @@
 import unittest
 
 from scalecodec.base import ScaleBytes, ScaleDecoder, RuntimeConfiguration
+from scalecodec.exceptions import InvalidScaleTypeValueException
 from scalecodec.type_registry import load_type_registry_preset, load_type_registry_file
 
 from scalecodec.types import CompactU32, Struct
@@ -335,6 +336,13 @@ def test_option_bytes_encode_decode(self):
 
         self.assertEqual(obj_check.decode(), value)
 
+    def test_option_decode_invalid(self):
+        obj = RuntimeConfiguration().create_scale_object('Option<Bytes>', ScaleBytes("0x0200"))
+        with self.assertRaisesRegex(
+            InvalidScaleTypeValueException, r"^Invalid starting byte for 'Option': '0x02'$"
+        ):
+            obj.decode()
+
     def test_proposal_encode_decode(self):
 
         value = {