diff --git a/CHANGES.rst b/CHANGES.rst
index f9a587f3181..23ace2d3bc1 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -58,3 +58,6 @@ Bugs fixed
 
 Testing
 -------
+
+* #13224: Correctness fixup for ``test_html_multi_line_copyright``.
+  Patch by Colin Watson, applied by James Addison.
diff --git a/tests/test_builders/test_build_html_copyright.py b/tests/test_builders/test_build_html_copyright.py
index 7a18bceb603..69ddd2d1f8a 100644
--- a/tests/test_builders/test_build_html_copyright.py
+++ b/tests/test_builders/test_build_html_copyright.py
@@ -9,6 +9,18 @@
 LOCALTIME_2009 = type(LT)(LT_NEW)
 
 
+@pytest.fixture
+def no_source_date_year(monkeypatch):
+    """
+    Explicitly clear SOURCE_DATE_EPOCH from the environment; this
+    fixture can be used to ensure that copyright substitution logic
+    does not occur during selected test cases.
+    """
+    with monkeypatch.context() as m:
+        m.delenv('SOURCE_DATE_EPOCH', raising=False)
+        yield
+
+
 @pytest.fixture(
     params=[
         1199145600,  # 2008-01-01 00:00:00
@@ -24,7 +36,7 @@ def source_date_year(request, monkeypatch):
 
 
 @pytest.mark.sphinx('html', testroot='copyright-multiline')
-def test_html_multi_line_copyright(app):
+def test_html_multi_line_copyright(no_source_date_year, app):
     app.build(force_all=True)
 
     content = (app.outdir / 'index.html').read_text(encoding='utf-8')