diff --git a/sphinx/application.py b/sphinx/application.py
index ba5aa2ca2..9e4831e1b 100644
--- a/sphinx/application.py
+++ b/sphinx/application.py
@@ -24,7 +24,6 @@ from six.moves import cStringIO
 
 import docutils
 from docutils import nodes
-from docutils.languages import get_language as docutils_get_language
 from docutils.parsers.rst import directives, roles
 
 import sphinx
@@ -108,14 +107,6 @@ ENV_PICKLE_FILENAME = 'environment.pickle'
 logger = logging.getLogger(__name__)
 
 
-# monkey patch docutils get_language
-def patched_docutils_get_language(language_code, reporter=None):  # NOQA
-    return docutils_get_language(language_code)
-
-
-docutils.languages.get_language = patched_docutils_get_language
-
-
 class Sphinx(object):
 
     def __init__(self, srcdir, confdir, outdir, doctreedir, buildername,
diff --git a/sphinx/cmdline.py b/sphinx/cmdline.py
index 650f88b44..7b6cf0860 100644
--- a/sphinx/cmdline.py
+++ b/sphinx/cmdline.py
@@ -24,7 +24,7 @@ from sphinx.errors import SphinxError
 from sphinx.application import Sphinx
 from sphinx.util import Tee, format_exception_cut_frames, save_traceback
 from sphinx.util.console import red, nocolor, color_terminal  # type: ignore
-from sphinx.util.docutils import docutils_namespace
+from sphinx.util.docutils import docutils_namespace, patch_docutils
 from sphinx.util.osutil import abspath, fs_encoding
 from sphinx.util.pycompat import terminal_safe
 
@@ -299,7 +299,7 @@ def main(argv):
 
     app = None
     try:
-        with docutils_namespace():
+        with patch_docutils(), docutils_namespace():
             app = Sphinx(srcdir, confdir, outdir, doctreedir, opts.builder,
                          confoverrides, status, warning, opts.freshenv,
                          opts.warningiserror, opts.tags, opts.verbosity, opts.jobs)
diff --git a/sphinx/setup_command.py b/sphinx/setup_command.py
index 8e773923f..d219a14d9 100644
--- a/sphinx/setup_command.py
+++ b/sphinx/setup_command.py
@@ -23,7 +23,7 @@ from distutils.errors import DistutilsOptionError, DistutilsExecError  # type: i
 from sphinx.application import Sphinx
 from sphinx.cmdline import handle_exception
 from sphinx.util.console import nocolor, color_terminal
-from sphinx.util.docutils import docutils_namespace
+from sphinx.util.docutils import docutils_namespace, patch_docutils
 from sphinx.util.osutil import abspath
 
 if False:
@@ -183,7 +183,7 @@ class BuildDoc(Command):
             app = None
 
             try:
-                with docutils_namespace():
+                with patch_docutils(), docutils_namespace():
                     app = Sphinx(self.source_dir, self.config_dir,
                                  builder_target_dir, self.doctree_dir,
                                  builder, confoverrides, status_stream,
diff --git a/sphinx/util/docutils.py b/sphinx/util/docutils.py
index 8bb0b3661..1fe72af58 100644
--- a/sphinx/util/docutils.py
+++ b/sphinx/util/docutils.py
@@ -13,9 +13,11 @@ from __future__ import absolute_import
 import re
 import types
 from copy import copy
+from distutils.version import LooseVersion
 from contextlib import contextmanager
 
 import docutils
+from docutils.languages import get_language
 from docutils.utils import Reporter
 from docutils.parsers.rst import directives, roles, convert_directive_function
 
@@ -34,7 +36,7 @@ if False:
     from sphinx.environment import BuildEnvironment  # NOQA
 
 
-__version_info__ = tuple(map(int, docutils.__version__.split('.')))
+__version_info__ = tuple(LooseVersion(docutils.__version__).version)
 
 
 @contextmanager
@@ -51,6 +53,29 @@ def docutils_namespace():
         roles._roles = _roles
 
 
+def patched_get_language(language_code, reporter=None):
+    # type: (unicode, Reporter) -> Any
+    """A wrapper for docutils.languages.get_language().
+
+    This ignores the second argument ``reporter`` to suppress warnings.
+    refs: https://github.com/sphinx-doc/sphinx/issues/3788
+    """
+    return get_language(language_code)
+
+
+@contextmanager
+def patch_docutils():
+    # type: () -> Iterator[None]
+    """Patch to docutils temporarily."""
+    try:
+        docutils.languages.get_language = patched_get_language
+
+        yield
+    finally:
+        # restore original implementations
+        docutils.languages.get_language = get_language
+
+
 class ElementLookupError(Exception):
     pass