diff --git a/docs/source/config_file.rst b/docs/source/config_file.rst
index dcd152328693..b110e530aa30 100644
--- a/docs/source/config_file.rst
+++ b/docs/source/config_file.rst
@@ -219,6 +219,10 @@ overridden by the pattern sections matching the module name.
 - ``disallow_any_generics`` (Boolean, default false) disallows usage of generic types that
   do not specify explicit type parameters.
 
+- ``disallow_incomplete_defs`` (Boolean, default false) disallow defining
+  functions with incomplete type annotations.  See
+  :ref:`--disallow-incomplete-defs <disallow-incomplete-defs>` option.
+
 - ``disallow_subclassing_any`` (Boolean, default False) disallows
   subclassing a value of type ``Any``.  See
   :ref:`--disallow-subclassing-any <disallow-subclassing-any>` option.
diff --git a/mypy/options.py b/mypy/options.py
index 3b07ed5fac5b..9171dd865cdd 100644
--- a/mypy/options.py
+++ b/mypy/options.py
@@ -18,32 +18,34 @@ class Options:
     """Options collected from flags."""
 
     PER_MODULE_OPTIONS = {
-        "ignore_missing_imports",
-        "follow_imports",
-        "follow_imports_for_stubs",
-        "disallow_any_generics",
-        "disallow_any_unimported",
-        "disallow_any_expr",
+        # Please keep this list sorted
+        "always_false",
+        "always_true",
+        "check_untyped_defs",
+        "debug_cache",
         "disallow_any_decorated",
         "disallow_any_explicit",
+        "disallow_any_expr",
+        "disallow_any_generics",
+        "disallow_any_unimported",
+        "disallow_incomplete_defs",
         "disallow_subclassing_any",
         "disallow_untyped_calls",
+        "disallow_untyped_decorators",
         "disallow_untyped_defs",
-        "check_untyped_defs",
-        "debug_cache",
-        "strict_optional_whitelist",
+        "follow_imports",
+        "follow_imports_for_stubs",
+        "ignore_errors",
+        "ignore_missing_imports",
+        "local_partial_types",
+        "no_implicit_optional",
         "show_none_errors",
+        "strict_boolean",
+        "strict_optional",
+        "strict_optional_whitelist",
         "warn_no_return",
         "warn_return_any",
         "warn_unused_ignores",
-        "ignore_errors",
-        "strict_boolean",
-        "no_implicit_optional",
-        "always_true",
-        "always_false",
-        "strict_optional",
-        "disallow_untyped_decorators",
-        "local_partial_types",
     }
 
     OPTIONS_AFFECTING_CACHE = ((PER_MODULE_OPTIONS |
diff --git a/test-data/unit/check-flags.test b/test-data/unit/check-flags.test
index 3cc5867416e7..4520fd3a5d71 100644
--- a/test-data/unit/check-flags.test
+++ b/test-data/unit/check-flags.test
@@ -471,6 +471,23 @@ if z:  # E: Condition must be a boolean
 [builtins fixtures/bool.pyi]
 
 
+[case testPerFileIncompleteDefsBasic]
+# flags: --config-file tmp/mypy.ini
+import standard, incomplete
+
+[file standard.py]
+def incomplete(x) -> int:
+    return 0
+[file incomplete.py]
+def incomplete(x) -> int:  # E: Function is missing a type annotation for one or more arguments
+    return 0
+[file mypy.ini]
+[[mypy]
+disallow_incomplete_defs = False
+[[mypy-incomplete]
+disallow_incomplete_defs = True
+
+
 [case testPerFileStrictOptionalBasic]
 # flags: --config-file tmp/mypy.ini
 import standard, optional