diff --git a/sphinx/ext/napoleon/docstring.py b/sphinx/ext/napoleon/docstring.py
index e526a11aeb..ef9ff1627c 100644
--- a/sphinx/ext/napoleon/docstring.py
+++ b/sphinx/ext/napoleon/docstring.py
@@ -27,7 +27,7 @@ _google_section_regex = re.compile(r'^(\s|\w)+:\s*$')
 _google_typed_arg_regex = re.compile(r'\s*(.+?)\s*\(\s*(.*[^\s]+)\s*\)')
 _numpy_section_regex = re.compile(r'^[=\-`:\'"~^_*+#<>]{2,}\s*$')
 _single_colon_regex = re.compile(r'(?<!:):(?!:)')
-_xref_regex = re.compile(r'(:\w+:\S+:`.+?`|:\S+:`.+?`|`.+?`)')
+_xref_regex = re.compile(r'(:(?:[a-zA-Z0-9]+[\-_+:.])*[a-zA-Z0-9]+:`.+?`)')
 _bullet_list_regex = re.compile(r'^(\*|\+|\-)(\s+\S|\s*$)')
 _enumerated_list_regex = re.compile(
     r'^(?P<paren>\()?'
diff --git a/tests/test_ext_napoleon.py b/tests/test_ext_napoleon.py
index 7ecd082923..21d095a797 100644
--- a/tests/test_ext_napoleon.py
+++ b/tests/test_ext_napoleon.py
@@ -68,6 +68,7 @@ class SampleError(Exception):
     def __special_undoc__(self):
         pass
 
+
 SampleNamedTuple = namedtuple('SampleNamedTuple', 'user_id block_type def_id')
 
 
diff --git a/tests/test_ext_napoleon_docstring.py b/tests/test_ext_napoleon_docstring.py
index 37dcca90c0..be9103063e 100644
--- a/tests/test_ext_napoleon_docstring.py
+++ b/tests/test_ext_napoleon_docstring.py
@@ -284,8 +284,9 @@ Construct a new XBlock.
 This class should only be used by runtimes.
 
 Arguments:
-    runtime (:class:`Runtime`): Use it to access the environment.
-        It is available in XBlock code as ``self.runtime``.
+    runtime (:class:`~typing.Dict`\[:class:`int`,:class:`str`\]): Use it to
+        access the environment. It is available in XBlock code
+        as ``self.runtime``.
 
     field_data (:class:`FieldData`): Interface used by the XBlock
         fields to access their data from wherever it is persisted.
@@ -300,9 +301,10 @@ Construct a new XBlock.
 
 This class should only be used by runtimes.
 
-:param runtime: Use it to access the environment.
-                It is available in XBlock code as ``self.runtime``.
-:type runtime: :class:`Runtime`
+:param runtime: Use it to
+                access the environment. It is available in XBlock code
+                as ``self.runtime``.
+:type runtime: :class:`~typing.Dict`\[:class:`int`,:class:`str`\]
 :param field_data: Interface used by the XBlock
                    fields to access their data from wherever it is persisted.
 :type field_data: :class:`FieldData`