diff --git a/CHANGES b/CHANGES
index f337471e3..b8ab15e8c 100644
--- a/CHANGES
+++ b/CHANGES
@@ -17,6 +17,7 @@ Bugs fixed
 ----------
 
 * #4669: sphinx.build_main and sphinx.make_main throw NameError
+* #4685: autosummary emits meaningless warnings
 
 Testing
 --------
diff --git a/sphinx/ext/autosummary/__init__.py b/sphinx/ext/autosummary/__init__.py
index 1334084e2..19046112a 100644
--- a/sphinx/ext/autosummary/__init__.py
+++ b/sphinx/ext/autosummary/__init__.py
@@ -78,7 +78,7 @@ from sphinx.ext.autodoc.directive import DocumenterBridge, Options
 from sphinx.ext.autodoc.importer import import_module
 from sphinx.pycode import ModuleAnalyzer, PycodeError
 from sphinx.util import import_object, rst, logging
-from sphinx.util.docutils import new_document
+from sphinx.util.docutils import NullReporter, new_document
 
 if TYPE_CHECKING:
     from typing import Any, Dict, List, Tuple, Type, Union  # NOQA
@@ -475,6 +475,7 @@ def extract_summary(doc, document):
         while sentences:
             summary += sentences.pop(0) + '.'
             node = new_document('', document.settings)
+            node.reporter = NullReporter()
             state_machine.run([summary], node)
             if not node.traverse(nodes.system_message):
                 # considered as that splitting by period does not break inline markups
diff --git a/sphinx/util/docutils.py b/sphinx/util/docutils.py
index 0fb544f49..a1ae3b31e 100644
--- a/sphinx/util/docutils.py
+++ b/sphinx/util/docutils.py
@@ -185,6 +185,14 @@ class LoggingReporter(Reporter):
                           stream, debug, error_handler=error_handler)
 
 
+class NullReporter(Reporter):
+    """A dummy reporter; write nothing."""
+
+    def __init__(self):
+        # type: () -> None
+        Reporter.__init__(self, '', 999, 4)
+
+
 def is_html5_writer_available():
     # type: () -> bool
     return __version_info__ > (0, 13, 0)
diff --git a/tests/test_ext_autosummary.py b/tests/test_ext_autosummary.py
index f9e217801..f988195a9 100644
--- a/tests/test_ext_autosummary.py
+++ b/tests/test_ext_autosummary.py
@@ -55,7 +55,7 @@ def test_mangle_signature():
         assert res == outp, (u"'%s' -> '%s' != '%s'" % (inp, res, outp))
 
 
-def test_extract_summary():
+def test_extract_summary(capsys):
     from sphinx.util.docutils import new_document
     from mock import Mock
     settings = Mock(language_code='',
@@ -77,6 +77,9 @@ def test_extract_summary():
            'it does not break sentence.']
     assert extract_summary(doc, document) == ' '.join(doc)
 
+    _, err = capsys.readouterr()
+    assert err == ''
+
 
 @pytest.mark.sphinx('dummy', **default_kw)
 def test_get_items_summary(make_app, app_params):