diff --git a/sphinx/config.py b/sphinx/config.py
index 0c0cad1fc..daa81f17e 100644
--- a/sphinx/config.py
+++ b/sphinx/config.py
@@ -395,8 +395,8 @@ def convert_source_suffix(app, config):
         # if dict, convert it to OrderedDict
         config.source_suffix = OrderedDict(config.source_suffix)  # type: ignore
     else:
-        logger.warning(__("The config value `source_suffix' expected to "
-                          "a string, list of strings or dictionary. "
+        logger.warning(__("The config value `source_suffix' expects "
+                          "a string, list of strings, or dictionary. "
                           "But `%r' is given." % source_suffix))
 
 
@@ -463,11 +463,16 @@ def check_confval_types(app, config):
                 continue  # at least we share a non-trivial base class
 
             if annotations:
-                msg = __("The config value `{name}' has type `{current.__name__}', "
-                         "expected to {permitted}.")
+                msg = __("The config value `{name}' has type `{current.__name__}'; "
+                         "expected {permitted}.")
+                wrapped_annotations = ["`{}'".format(c.__name__) for c in annotations]
+                if len(wrapped_annotations) > 2:
+                    permitted = ", ".join(wrapped_annotations[:-1]) + ", or " + wrapped_annotations[-1]
+                else:
+                    permitted = " or ".join(wrapped_annotations)
                 logger.warning(msg.format(name=confval.name,
                                           current=type(confval.value),
-                                          permitted=str([c.__name__ for c in annotations])))
+                                          permitted=permitted))
             else:
                 msg = __("The config value `{name}' has type `{current.__name__}', "
                          "defaults to `{default.__name__}'.")
diff --git a/tests/test_config.py b/tests/test_config.py
index bf69c40e5..f8df52863 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -247,6 +247,27 @@ def test_check_types(logger, name, default, annotation, actual, warned):
     assert logger.warning.called == warned
 
 
+TYPECHECK_WARNING_MESSAGES = [
+    ('value1', 'string', [str], ['foo', 'bar'],
+        "The config value `value1' has type `list'; expected `str'."),
+    ('value1', 'string', [str, int], ['foo', 'bar'],
+        "The config value `value1' has type `list'; expected `str' or `int'."),
+    ('value1', 'string', [str, int, tuple], ['foo', 'bar'],
+        "The config value `value1' has type `list'; expected `str', `int', or `tuple'."),
+]
+
+
+@mock.patch("sphinx.config.logger")
+@pytest.mark.parametrize("name,default,annotation,actual,message", TYPECHECK_WARNING_MESSAGES)
+def test_conf_warning_message(logger, name, default, annotation, actual, message):
+    config = Config({name: actual})
+    config.add(name, default, False, annotation or ())
+    config.init_values()
+    check_confval_types(None, config)
+    logger.warning.assert_called()
+    assert logger.warning.call_args[0][0] == message
+
+
 @mock.patch("sphinx.config.logger")
 def test_check_enum(logger):
     config = Config()