diff --git a/tests/test_read.py b/tests/test_read.py
index b2c4a1f..b5d4f69 100644
--- a/tests/test_read.py
+++ b/tests/test_read.py
@@ -1,6 +1,4 @@
-import os
 import pytest
-import sys
 from io import StringIO
 
 from wosfile.read import (
@@ -97,6 +95,12 @@ def test_forgotten_EF(self):
         with pytest.raises(ReadError):
             list(r)
 
+    def test_unknown_tag(self):
+        f = StringIO(preamble_s + "PT abc\n\nQQ x\nER\nEF")
+        r = PlainTextReader(f)
+        with pytest.raises(NotImplementedError):
+            list(r)
+
     def test_ignore_empty_lines(self):
         f = StringIO(preamble_s + "PT abc\n\nAU xyz\nER\nEF")
         r = PlainTextReader(f)
diff --git a/tests/test_record.py b/tests/test_record.py
index 9ad4bf5..0204f59 100644
--- a/tests/test_record.py
+++ b/tests/test_record.py
@@ -66,6 +66,11 @@ def test_record_author_address(data, record_id, author_address):
     assert rec.author_address == author_address
 
 
+def test_record_author_address_missing():
+    rec = Record({})
+    assert rec.author_address is None
+
+
 addresses = [
     # (input, expected, exception)
     (
diff --git a/wosfile/read.py b/wosfile/read.py
index cf1add4..2d75704 100644
--- a/wosfile/read.py
+++ b/wosfile/read.py
@@ -1,7 +1,6 @@
 import codecs
 import logging
 import pathlib
-import sys
 from csv import DictReader
 from typing import (
     AnyStr,
@@ -217,11 +216,13 @@ def _format_values(self, heading: str, values: List[str]) -> str:
             else:
                 return " ".join(values)
         except KeyError:
-            msg = "\n------------ ERROR ------------\n" \
-                "Seems that the tag \"{}\" is new and not yet handled by the wosfile library.\n" \
-                "Please report this error:\n" \
-                "  https://github.com/rafguns/wosfile/issues\n" \
+            msg = (
+                "\n------------ ERROR ------------\n"
+                'Seems that the tag "{}" is new and not yet handled by the wosfile library.\n'
+                "Please report this error:\n"
+                "  https://github.com/rafguns/wosfile/issues\n"
                 "We are sorry for the inconvenience.\n"
+            )
             raise NotImplementedError(msg.format(heading))
 
     def __next__(self) -> Dict[str, str]:
diff --git a/wosfile/record.py b/wosfile/record.py
index 51b265e..d180f8e 100644
--- a/wosfile/record.py
+++ b/wosfile/record.py
@@ -22,6 +22,7 @@ def __init__(
         :param bool skip_empty: whether or not to skip empty fields
 
         """
+        super().__init__(self)
         self.skip_empty = skip_empty
         if wos_data:
             self.parse(wos_data)