diff --git a/CHANGES.rst b/CHANGES.rst
index 03c8201..4460529 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,3 +1,7 @@
+0.15.2 (2022-01-12)
+-------------------
+- fix #408
+
 0.15.1 (2021-12-20)
 -------------------
 - Multi-rendering with same DocxTemplate object is now possible
diff --git a/docxtpl/__init__.py b/docxtpl/__init__.py
index 8a64502..8b2fcfc 100644
--- a/docxtpl/__init__.py
+++ b/docxtpl/__init__.py
@@ -4,7 +4,7 @@ Created : 2015-03-12
 
 @author: Eric Lapouyade
 """
-__version__ = '0.15.1'
+__version__ = '0.15.2'
 
 # flake8: noqa
 from .inline_image import InlineImage
diff --git a/docxtpl/template.py b/docxtpl/template.py
index b615f80..3c97202 100644
--- a/docxtpl/template.py
+++ b/docxtpl/template.py
@@ -715,6 +715,7 @@ class DocxTemplate(object):
         self.is_saved = True
 
     def get_undeclared_template_variables(self, jinja_env=None):
+        self.init_docx()
         xml = self.get_xml()
         xml = self.patch_xml(xml)
         for uri in [self.HEADER_URI, self.FOOTER_URI]: