diff --git a/pyproject.toml b/pyproject.toml
index f74b40b..5e35e6d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -17,7 +17,7 @@ namespaces = true
 # ----------------------------------------- Project Metadata -------------------------------------
 #
 [project]
-version = "0.0.0.dev12"
+version = "0.0.0.dev13"
 name = "LicenseMan"
 requires-python = ">=3.10"
 dependencies = [
diff --git a/src/licenseman/spdx/license.py b/src/licenseman/spdx/license.py
index 74cc716..6be71ee 100644
--- a/src/licenseman/spdx/license.py
+++ b/src/licenseman/spdx/license.py
@@ -96,12 +96,12 @@ def header_html(self) -> str | None:
         return self._data.get("standardLicenseHeaderHtml")
 
     @property
-    def header_xml(self) -> _ElementTree.Element:
+    def header_xml(self) -> _ElementTree.Element | None:
         return self._xml.find('.//standardLicenseHeader', self._ns)
 
     @property
-    def header_xml_str(self) -> str:
-        return self._xml_str(self.header_xml)
+    def header_xml_str(self) -> str | None:
+        return self._xml_str(self.header_xml) if self.header_xml else None
 
     @property
     def cross_refs(self) -> list[SPDXLicenseCrossRef]: