diff --git a/sphinx/config.py b/sphinx/config.py
index 5675cfba3..22b98a834 100644
--- a/sphinx/config.py
+++ b/sphinx/config.py
@@ -610,7 +610,7 @@ def _substitute_copyright_year(copyright_line: str, replace_year: str) -> str:
     if copyright_line[4] != '-':
         return copyright_line
 
-    if copyright_line[5:9].isdigit() and copyright_line[9] in ' ,':
+    if copyright_line[5:9].isdigit() and copyright_line[9:10] in {'', ' ', ','}:
         return copyright_line[:5] + replace_year + copyright_line[9:]
 
     return copyright_line
diff --git a/tests/test_config/test_config.py b/tests/test_config/test_config.py
index 317a50bf3..ee305274e 100644
--- a/tests/test_config/test_config.py
+++ b/tests/test_config/test_config.py
@@ -8,7 +8,13 @@ import pytest
 
 import sphinx
 from sphinx.builders.gettext import _gettext_compact_validator
-from sphinx.config import ENUM, Config, _Opt, check_confval_types
+from sphinx.config import (
+    ENUM,
+    Config,
+    _Opt,
+    check_confval_types,
+    correct_copyright_year,
+)
 from sphinx.deprecation import RemovedInSphinx90Warning
 from sphinx.errors import ConfigError, ExtensionError, VersionRequirementError
 
@@ -556,6 +562,24 @@ def test_multi_line_copyright(source_date_year, app, monkeypatch):
         ) in content
 
 
+@pytest.mark.parametrize(('conf_copyright', 'expected_copyright'), [
+    ('1970', '{current_year}'),
+    # https://github.com/sphinx-doc/sphinx/issues/11913
+    ('1970-1990', '1970-{current_year}'),
+    ('1970-1990 Alice', '1970-{current_year} Alice'),
+])
+def test_correct_copyright_year(conf_copyright, expected_copyright, source_date_year):
+    config = Config({}, {'copyright': conf_copyright})
+    correct_copyright_year(_app=None, config=config)
+    actual_copyright = config['copyright']
+
+    if source_date_year is None:
+        expected_copyright = conf_copyright
+    else:
+        expected_copyright = expected_copyright.format(current_year=source_date_year)
+    assert actual_copyright == expected_copyright
+
+
 def test_gettext_compact_command_line_true():
     config = Config({}, {'gettext_compact': '1'})
     config.add('gettext_compact', True, '', {bool, str})