diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index f1f5630..b5896d3 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -6,6 +6,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+[v0.12.4] - 2023-12-12
+---------------------
+
+Fixed
+~~~~~
+
+* TypeError: cannot unpack non-iterable NoneType object in `_parse_ref_system` method.
 
 
 [v0.12.3] - 2023-12-12
diff --git a/ows_lib/__init__.py b/ows_lib/__init__.py
index 2a96dd5..b2a0a13 100644
--- a/ows_lib/__init__.py
+++ b/ows_lib/__init__.py
@@ -1,2 +1,2 @@
-__version__ = "0.12.3"
+__version__ = "0.12.4"
 VERSION = __version__  # synonym
diff --git a/ows_lib/xml_mapper/iso_metadata/iso_metadata.py b/ows_lib/xml_mapper/iso_metadata/iso_metadata.py
index 4394196..1f08e5b 100644
--- a/ows_lib/xml_mapper/iso_metadata/iso_metadata.py
+++ b/ows_lib/xml_mapper/iso_metadata/iso_metadata.py
@@ -126,7 +126,7 @@ def _parse_ref_system(self):
 
             return code, prefix
         else:
-            return None
+            return None, None
 
     @property
     def code(self):