diff --git a/CHANGES.rst b/CHANGES.rst
index 57d0c26..603460c 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -4,7 +4,9 @@ Changes
 4.2.1 (unreleased)
 ------------------
 
-- Nothing changed yet.
+- Fix ``GlobalObject`` (and ``GlobalInterface``) no longer allowing
+  just a single '.'. See `issue 35
+  <https://github.com/zopefoundation/zope.configuration/issues/35>`_.
 
 
 4.2.0 (2018-09-26)
diff --git a/src/zope/configuration/fields.py b/src/zope/configuration/fields.py
index e934f69..70527a5 100644
--- a/src/zope/configuration/fields.py
+++ b/src/zope/configuration/fields.py
@@ -35,7 +35,11 @@ from zope.configuration.interfaces import InvalidToken
 
 class PythonIdentifier(schema_PythonIdentifier):
     """
-    This class is like `zope.schema.PythonIdentifier`, but does not allow empty strings.
+    This class is like `zope.schema.PythonIdentifier`.
+
+    .. versionchanged:: 4.2.0
+       Extend `zope.schema.PythonIdentifier`, which implies that `fromUnicode`
+       validates the strings.
     """
 
     def _validate(self, value):
@@ -73,9 +77,12 @@ class GlobalObject(Field):
 
         try:
             # Leading dots are allowed here to indicate current
-            # package.
+            # package, but not accepted by DottedName. Take care,
+            # though, because a single dot is valid to resolve, but
+            # not valid to pass to DottedName (as an empty string)
             to_validate = name[1:] if name.startswith('.') else name
-            self._DOT_VALIDATOR.validate(to_validate)
+            if to_validate:
+                self._DOT_VALIDATOR.validate(to_validate)
         except ValidationError as v:
             v.with_field_and_value(self, name)
             raise

Regression in 4.2: GlobalObject fields no longer allow just "."
This shows up in `zope.preference`:
```xml
<configure
    xmlns="http://namespaces.zope.org/zope"
    xmlns:apidoc="http://namespaces.zope.org/apidoc"
    xmlns:zcml="http://namespaces.zope.org/zcml"
    i18n_domain="zope"
    >

  <include package="zope.component" file="meta.zcml" />
  <include package="." file="meta.zcml" />  <!-- Line 9 -->
```

Loading its `configure.zcml` results in:
```
 File "//eggs/zope.configuration-4.2.0-py2.7.egg/zope/configuration/config.py", line 817, in toargs
    args[str(name)] = field.fromUnicode(s)
  File "//zope.configuration-4.2.0-py2.7.egg/zope/configuration/fields.py", line 78, in fromUnicode
    self._DOT_VALIDATOR.validate(to_validate)
  File "//zope.schema-4.9.0-py2.7.egg/zope/schema/_bootstrapfields.py", line 291, in validate
    self._validate(value)
  File "/zope.schema-4.9.0-py2.7.egg/zope/schema/_field.py", line 670, in _validate
    raise InvalidDottedName(value).with_field_and_value(self, value)
zope.configuration.xmlconfig.ZopeXMLConfigurationError: File "/.../configure.zcml", line 40.1-40.38
    ZopeXMLConfigurationError: File "/...buildout/eggs/zope.preference-4.0.0-py2.7.egg/zope/preference/configure.zcml", line 9.2-9.42
    ConfigurationError: ('Invalid value for', 'package', '')
```
diff --git a/src/zope/configuration/tests/test_fields.py b/src/zope/configuration/tests/test_fields.py
index 734572e..6964957 100644
--- a/src/zope/configuration/tests/test_fields.py
+++ b/src/zope/configuration/tests/test_fields.py
@@ -92,9 +92,23 @@ class GlobalObjectTests(unittest.TestCase, _ConformsToIFromUnicode):
         context = Context()
         bound = go.bind(context)
         found = bound.fromUnicode('tried')
-        self.assertTrue(found is _target)
+        self.assertIs(found, _target)
         self.assertEqual(context._resolved, 'tried')
 
+    def test_fromUnicode_w_resolve_dot(self):
+        _target = object()
+        class Context(object):
+            _resolved = None
+            def resolve(self, name):
+                self._resolved = name
+                return _target
+        go = self._makeOne()
+        context = Context()
+        bound = go.bind(context)
+        found = bound.fromUnicode('.')
+        self.assertIs(found, _target)
+        self.assertEqual(context._resolved, '.')
+
     def test_fromUnicode_w_resolve_but_validation_fails(self):
         from zope.schema import Text
         from zope.schema import ValidationError

pip install -e .[dev]
parse_log_pytest
requirements.txt
nose coverage Sphinx pytest
3.9
requirements/base.txt
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
alabaster==0.7.16
babel==2.17.0
certifi==2025.1.31
charset-normalizer==3.4.1
coverage==7.8.0
docutils==0.21.2
exceptiongroup==1.2.2
idna==3.10
imagesize==1.4.1
importlib_metadata==8.6.1
iniconfig==2.1.0
Jinja2==3.1.6
MarkupSafe==3.0.2
nose==1.3.7
packaging==24.2
pluggy==1.5.0
Pygments==2.19.1
pytest==8.3.5
requests==2.32.3
snowballstemmer==2.2.0
Sphinx==7.4.7
sphinxcontrib-applehelp==2.0.0
sphinxcontrib-devhelp==2.0.0
sphinxcontrib-htmlhelp==2.1.0
sphinxcontrib-jsmath==1.0.1
sphinxcontrib-qthelp==2.0.0
sphinxcontrib-serializinghtml==2.0.0
tomli==2.2.1
urllib3==2.3.0
zipp==3.21.0
-e git+https://github.com/zopefoundation/zope.configuration.git@abac0539cfae8365ca69b949983f588ec9bbfe52#egg=zope.configuration
zope.event==5.0
zope.i18nmessageid==7.0
zope.interface==7.2
zope.schema==7.0.1

name: zope.configuration
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - ca-certificates=2025.2.25=h06a4308_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.4.4=h6a678d5_1
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - ncurses=6.4=h6a678d5_0
  - openssl=3.0.16=h5eee18b_0
  - pip=25.0=py39h06a4308_0
  - python=3.9.21=he870216_1
  - readline=8.2=h5eee18b_0
  - setuptools=75.8.0=py39h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - tzdata=2025a=h04d1e81_0
  - wheel=0.45.1=py39h06a4308_0
  - xz=5.6.4=h5eee18b_1
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - alabaster==0.7.16
      - babel==2.17.0
      - certifi==2025.1.31
      - charset-normalizer==3.4.1
      - coverage==7.8.0
      - docutils==0.21.2
      - exceptiongroup==1.2.2
      - idna==3.10
      - imagesize==1.4.1
      - importlib-metadata==8.6.1
      - iniconfig==2.1.0
      - jinja2==3.1.6
      - markupsafe==3.0.2
      - nose==1.3.7
      - packaging==24.2
      - pluggy==1.5.0
      - pygments==2.19.1
      - pytest==8.3.5
      - requests==2.32.3
      - snowballstemmer==2.2.0
      - sphinx==7.4.7
      - sphinxcontrib-applehelp==2.0.0
      - sphinxcontrib-devhelp==2.0.0
      - sphinxcontrib-htmlhelp==2.1.0
      - sphinxcontrib-jsmath==1.0.1
      - sphinxcontrib-qthelp==2.0.0
      - sphinxcontrib-serializinghtml==2.0.0
      - tomli==2.2.1
      - urllib3==2.3.0
      - zipp==3.21.0
      - zope-event==5.0
      - zope-i18nmessageid==7.0
      - zope-interface==7.2
      - zope-schema==7.0.1
prefix: /opt/conda/envs/zope.configuration

src/zope/configuration/tests/test_fields.py::GlobalObjectTests::test_fromUnicode_w_resolve_dot
src/zope/configuration/tests/test_fields.py::GlobalObjectTests::test__validate_w_value_type src/zope/configuration/tests/test_fields.py::GlobalObjectTests::test__validate_wo_value_type src/zope/configuration/tests/test_fields.py::GlobalObjectTests::test_class_conforms_to_IFromUnicode src/zope/configuration/tests/test_fields.py::GlobalObjectTests::test_fromUnicode_rejects_slash src/zope/configuration/tests/test_fields.py::GlobalObjectTests::test_fromUnicode_w_resolve_but_validation_fails src/zope/configuration/tests/test_fields.py::GlobalObjectTests::test_fromUnicode_w_resolve_fails src/zope/configuration/tests/test_fields.py::GlobalObjectTests::test_fromUnicode_w_resolve_success src/zope/configuration/tests/test_fields.py::GlobalObjectTests::test_fromUnicode_w_star_and_extra_ws src/zope/configuration/tests/test_fields.py::GlobalObjectTests::test_instance_conforms_to_IFromUnicode src/zope/configuration/tests/test_fields.py::GlobalInterfaceTests::test_class_conforms_to_IFromUnicode src/zope/configuration/tests/test_fields.py::GlobalInterfaceTests::test_ctor src/zope/configuration/tests/test_fields.py::GlobalInterfaceTests::test_instance_conforms_to_IFromUnicode src/zope/configuration/tests/test_fields.py::TokensTests::test_class_conforms_to_IFromUnicode src/zope/configuration/tests/test_fields.py::TokensTests::test_fromUnicode_empty src/zope/configuration/tests/test_fields.py::TokensTests::test_fromUnicode_invalid src/zope/configuration/tests/test_fields.py::TokensTests::test_fromUnicode_strips_ws src/zope/configuration/tests/test_fields.py::TokensTests::test_instance_conforms_to_IFromUnicode src/zope/configuration/tests/test_fields.py::PathTests::test_class_conforms_to_IFromUnicode src/zope/configuration/tests/test_fields.py::PathTests::test_fromUnicode_absolute src/zope/configuration/tests/test_fields.py::PathTests::test_fromUnicode_relative src/zope/configuration/tests/test_fields.py::PathTests::test_instance_conforms_to_IFromUnicode src/zope/configuration/tests/test_fields.py::BoolTests::test_class_conforms_to_IFromUnicode src/zope/configuration/tests/test_fields.py::BoolTests::test_fromUnicode_w_false_values src/zope/configuration/tests/test_fields.py::BoolTests::test_fromUnicode_w_invalid src/zope/configuration/tests/test_fields.py::BoolTests::test_fromUnicode_w_true_values src/zope/configuration/tests/test_fields.py::BoolTests::test_instance_conforms_to_IFromUnicode src/zope/configuration/tests/test_fields.py::MessageIDTests::test_class_conforms_to_IFromUnicode src/zope/configuration/tests/test_fields.py::MessageIDTests::test_domain_decodes_bytes src/zope/configuration/tests/test_fields.py::MessageIDTests::test_instance_conforms_to_IFromUnicode src/zope/configuration/tests/test_fields.py::MessageIDTests::test_w_empty_id src/zope/configuration/tests/test_fields.py::MessageIDTests::test_w_id_and_default src/zope/configuration/tests/test_fields.py::MessageIDTests::test_wo_domain src/zope/configuration/tests/test_fields.py::test_suite
src/zope/configuration/fields.py CHANGES.rst
src/zope/configuration/fields.py CHANGES.rst