diff --git a/sphinx/directives/__init__.py b/sphinx/directives/__init__.py
index f9d7497f9..f42e2cdf9 100644
--- a/sphinx/directives/__init__.py
+++ b/sphinx/directives/__init__.py
@@ -39,7 +39,7 @@ if False:
     from sphinx.config import Config  # NOQA
     from sphinx.environment import BuildEnvironment  # NOQA
     from sphinx.util.docfields import Field  # NOQA
-    from sphinx.util.typing import unicode  # NOQA
+    from sphinx.util.typing import DirectiveOption, unicode  # NOQA
 
 
 # RE to strip backslash escapes
@@ -60,7 +60,7 @@ class ObjectDescription(SphinxDirective):
     final_argument_whitespace = True
     option_spec = {
         'noindex': directives.flag,
-    }
+    }  # type: Dict[str, DirectiveOption]
 
     # types of doc fields that this directive handles, see sphinx.util.docfields
     doc_field_types = []    # type: List[Field]
diff --git a/sphinx/util/typing.py b/sphinx/util/typing.py
index e0cf0104b..d31b6044a 100644
--- a/sphinx/util/typing.py
+++ b/sphinx/util/typing.py
@@ -9,7 +9,7 @@
     :license: BSD, see LICENSE for details.
 """
 
-from typing import Callable, Dict, List, Tuple, TypeVar
+from typing import Any, Callable, Dict, List, Tuple, TypeVar
 
 from docutils import nodes
 from docutils.parsers.rst.states import Inliner
@@ -26,6 +26,8 @@ else:
 
 N_co = TypeVar('N_co', bound=nodes.Node, covariant=True)
 
+# An entry of Directive.option_spec
+DirectiveOption = Callable[[str], Any]
 
 # common role functions
 RoleFunction = Callable[[text_type, text_type, text_type, int, Inliner, Dict, List[text_type]],