diff --git a/AUTHORS.md b/AUTHORS.md
index 80a24d3be..f5b981b8e 100644
--- a/AUTHORS.md
+++ b/AUTHORS.md
@@ -266,5 +266,6 @@ Authors
 * [Yomna](https://github.com/ynasser)
 * [Yoni Jah](https://github.com/yonjah)
 * [YourDaddyIsHere](https://github.com/YourDaddyIsHere)
+* [Yuseong Cho](https://github.com/g6123)
 * [Zach Shepherd](https://github.com/zjs)
 * [陈三](https://github.com/chenxsan)
diff --git a/certbot-nginx/certbot_nginx/_internal/parser.py b/certbot-nginx/certbot_nginx/_internal/parser.py
index f71d7c018..0c1151826 100644
--- a/certbot-nginx/certbot_nginx/_internal/parser.py
+++ b/certbot-nginx/certbot_nginx/_internal/parser.py
@@ -2,6 +2,7 @@
 import copy
 import functools
 import glob
+import io
 import logging
 import re
 
@@ -205,12 +206,16 @@ class NginxParser(object):
             if item in self.parsed and not override:
                 continue
             try:
-                with open(item) as _file:
+                with io.open(item, "r", encoding="utf-8") as _file:
                     parsed = nginxparser.load(_file)
                     self.parsed[item] = parsed
                     trees.append(parsed)
             except IOError:
                 logger.warning("Could not open file: %s", item)
+            except UnicodeDecodeError:
+                logger.warning("Could not read file: %s due to invalid "
+                               "character. Only UTF-8 encoding is "
+                               "supported.", item)
             except pyparsing.ParseException as err:
                 logger.debug("Could not parse file: %s due to %s", item, err)
         return trees
@@ -414,10 +419,13 @@ class NginxParser(object):
 def _parse_ssl_options(ssl_options):
     if ssl_options is not None:
         try:
-            with open(ssl_options) as _file:
+            with io.open(ssl_options, "r", encoding="utf-8") as _file:
                 return nginxparser.load(_file)
         except IOError:
             logger.warning("Missing NGINX TLS options file: %s", ssl_options)
+        except UnicodeDecodeError:
+            logger.warning("Could not read file: %s due to invalid character. "
+                           "Only UTF-8 encoding is supported.", ssl_options)
         except pyparsing.ParseBaseException as err:
             logger.debug("Could not parse file: %s due to %s", ssl_options, err)
     return []
diff --git a/certbot-nginx/tests/parser_test.py b/certbot-nginx/tests/parser_test.py
index f3a5665c5..fd5d338d3 100644
--- a/certbot-nginx/tests/parser_test.py
+++ b/certbot-nginx/tests/parser_test.py
@@ -482,7 +482,43 @@ class NginxParserTest(util.NginxTest):
                 called = True
         self.assertTrue(called)
 
+    def test_valid_unicode_characters(self):
+        nparser = parser.NginxParser(self.config_path)
+        path = nparser.abs_path('valid_unicode_comments.conf')
+        parsed = nparser._parse_files(path)  # pylint: disable=protected-access
+        self.assertEqual(['server'], parsed[0][2][0])
+        self.assertEqual(['listen', '80'], parsed[0][2][1][3])
 
+    def test_invalid_unicode_characters(self):
+        with self.assertLogs() as log:
+            nparser = parser.NginxParser(self.config_path)
+            path = nparser.abs_path('invalid_unicode_comments.conf')
+            parsed = nparser._parse_files(path)  # pylint: disable=protected-access
+
+        self.assertEqual([], parsed)
+        self.assertTrue(any(
+            ('invalid character' in output) and ('UTF-8' in output)
+            for output in log.output
+        ))
+
+    def test_valid_unicode_characters_in_ssl_options(self):
+        nparser = parser.NginxParser(self.config_path)
+        path = nparser.abs_path('valid_unicode_comments.conf')
+        parsed = parser._parse_ssl_options(path)  # pylint: disable=protected-access
+        self.assertEqual(['server'], parsed[2][0])
+        self.assertEqual(['listen', '80'], parsed[2][1][3])
+
+    def test_invalid_unicode_characters_in_ssl_options(self):
+        with self.assertLogs() as log:
+            nparser = parser.NginxParser(self.config_path)
+            path = nparser.abs_path('invalid_unicode_comments.conf')
+            parsed = parser._parse_ssl_options(path)  # pylint: disable=protected-access
+
+        self.assertEqual([], parsed)
+        self.assertTrue(any(
+            ('invalid character' in output) and ('UTF-8' in output)
+            for output in log.output
+        ))
 
 if __name__ == "__main__":
     unittest.main()  # pragma: no cover
diff --git a/certbot-nginx/tests/test_log_util.py b/certbot-nginx/tests/test_log_util.py
new file mode 100644
index 000000000..7aebf2151
--- /dev/null
+++ b/certbot-nginx/tests/test_log_util.py
@@ -0,0 +1,125 @@
+"""Backport for `TestCase.assertLogs()`.
+
+Most of the idea and code are from CPython implementation.
+https://github.com/python/cpython/blob/b76518d43fb82ed9e5d27025d18c90a23d525c90/Lib/unittest/case.py
+"""
+import logging
+import collections
+
+__all__ = ['AssertLogsMixin']
+
+LoggingWatcher = collections.namedtuple('LoggingWatcher', ['records', 'output'])
+
+
+class CapturingHandler(logging.Handler):
+    """
+    A logging handler capturing all (raw and formatted) logging output.
+    """
+
+    def __init__(self):
+        super(CapturingHandler, self).__init__()
+        self.watcher = LoggingWatcher([], [])
+
+    def flush(self):
+        pass
+
+    def emit(self, record):
+        self.watcher.records.append(record)
+        self.watcher.output.append(self.format(record))
+
+
+
+class AssertLogsContext(object):
+    """
+    A context manager used to implement `TestCase.assertLogs()`.
+    """
+
+    LOGGING_FORMAT = '%(levelname)s:%(name)s:%(message)s'
+
+    def __init__(self, test_case, logger_name, level):
+        self.test_case = test_case
+
+        self.logger_name = logger_name
+        self.logger_states = None
+        self.logger = None
+
+        if level:
+            # pylint: disable=protected-access,no-member
+            try:
+                # In Python 3.x
+                name_to_level = logging._nameToLevel  # type: ignore
+            except AttributeError:
+                # In Python 2.7
+                name_to_level = logging._levelNames  # type: ignore
+
+            self.level = name_to_level.get(level, level)
+        else:
+            self.level = logging.INFO
+
+        self.watcher = None
+
+    def _save_logger_states(self):
+        self.logger_states = (self.logger.handlers[:], self.logger.level, self.logger.propagate)
+
+    def _restore_logger_states(self):
+        self.logger.handlers, self.logger.level, self.logger.propagate = self.logger_states
+
+    def __enter__(self):
+        if isinstance(self.logger_name, logging.Logger):
+            self.logger = self.logger_name
+        else:
+            self.logger = logging.getLogger(self.logger_name)
+
+        formatter = logging.Formatter(self.LOGGING_FORMAT)
+
+        handler = CapturingHandler()
+        handler.setFormatter(formatter)
+
+        self._save_logger_states()
+        self.logger.handlers = [handler]
+        self.logger.setLevel(self.level)
+        self.logger.propagate = False
+
+        self.watcher = handler.watcher
+        return handler.watcher
+
+    def __exit__(self, exc_type, exc_value, tb):
+        self._restore_logger_states()
+
+        if exc_type is not None:
+            # let unexpected exceptions pass through
+            return
+
+        if not self.watcher.records:
+            self._raiseFailure(
+                "no logs of level {} or higher triggered on {}"
+                .format(logging.getLevelName(self.level), self.logger.name))
+
+    def _raiseFailure(self, message):
+        message = self.test_case._formatMessage(None, message)  # pylint: disable=protected-access
+        raise self.test_case.failureException(message)
+
+
+class AssertLogsMixin(object):
+    """
+    A mixin that implements `TestCase.assertLogs()`.
+    """
+
+    def assertLogs(self, logger=None, level=None):
+        """Fail unless a log message of level *level* or higher is emitted
+        on *logger_name* or its children.  If omitted, *level* defaults to
+        INFO and *logger* defaults to the root logger.
+        This method must be used as a context manager, and will yield
+        a recording object with two attributes: `output` and `records`.
+        At the end of the context manager, the `output` attribute will
+        be a list of the matching formatted log messages and the
+        `records` attribute will be a list of the corresponding LogRecord
+        objects.
+        Example::
+            with self.assertLogs('foo', level='INFO') as cm:
+                logging.getLogger('foo').info('first message')
+                logging.getLogger('foo.bar').error('second message')
+            self.assertEqual(cm.output, ['INFO:foo:first message',
+                                         'ERROR:foo.bar:second message'])
+        """
+        return AssertLogsContext(self, logger, level)
diff --git a/certbot-nginx/tests/test_util.py b/certbot-nginx/tests/test_util.py
index 8dfd18637..4c9da84bd 100644
--- a/certbot-nginx/tests/test_util.py
+++ b/certbot-nginx/tests/test_util.py
@@ -14,9 +14,10 @@ from certbot.plugins import common
 from certbot.tests import util as test_util
 from certbot_nginx._internal import configurator
 from certbot_nginx._internal import nginxparser
+import test_log_util
 
 
-class NginxTest(test_util.ConfigTestCase):
+class NginxTest(test_log_util.AssertLogsMixin, test_util.ConfigTestCase):
 
     def setUp(self):
         super(NginxTest, self).setUp()
diff --git a/certbot-nginx/tests/testdata/etc_nginx/invalid_unicode_comments.conf b/certbot-nginx/tests/testdata/etc_nginx/invalid_unicode_comments.conf
new file mode 100644
index 000000000..4d6384535
--- /dev/null
+++ b/certbot-nginx/tests/testdata/etc_nginx/invalid_unicode_comments.conf
@@ -0,0 +1,7 @@
+# This configuration file is saved with EUC-KR (a.k.a. cp949) encoding,
+# including some Korean letters.
+
+server {
+    # �ȳ��ϼ���. 80�� ��Ʈ���� ��û�� ��ٸ���.
+    listen	80;
+}
diff --git a/certbot-nginx/tests/testdata/etc_nginx/valid_unicode_comments.conf b/certbot-nginx/tests/testdata/etc_nginx/valid_unicode_comments.conf
new file mode 100644
index 000000000..89c978b2e
--- /dev/null
+++ b/certbot-nginx/tests/testdata/etc_nginx/valid_unicode_comments.conf
@@ -0,0 +1,9 @@
+# This configuration file is saved with valid UTF-8 encoding,
+# including some CJK alphabets.
+
+server {
+    # 안녕하세요. 80번 포트에서 요청을 기다린다.
+    # こんにちは。８０番ポートからリクエストを待つ。
+    # 你好。等待端口80上的请求。
+    listen	80;
+}
diff --git a/certbot/CHANGELOG.md b/certbot/CHANGELOG.md
index 0bbc9b7ff..c35af0d0f 100644
--- a/certbot/CHANGELOG.md
+++ b/certbot/CHANGELOG.md
@@ -22,6 +22,8 @@ Certbot adheres to [Semantic Versioning](https://semver.org/).
 
 * When using an RFC 8555 compliant endpoint, the `acme` library no longer sends the
   `resource` field in any requests or the `type` field when responding to challenges.
+* Fix nginx plugin crash when non-ASCII configuration file is being read (instead,
+  the user will be warned that UTF-8 must be used).
 
 More details about these changes can be found on our GitHub repo.