diff --git a/gis_metadata/metadata_parser.py b/gis_metadata/metadata_parser.py
index 9f32e68..27543a3 100644
--- a/gis_metadata/metadata_parser.py
+++ b/gis_metadata/metadata_parser.py
@@ -11,9 +11,8 @@
 from gis_metadata.utils import DATES, DATE_TYPE, DATE_VALUES
 from gis_metadata.utils import DATE_TYPE_RANGE, DATE_TYPE_RANGE_BEGIN, DATE_TYPE_RANGE_END
 from gis_metadata.utils import parse_complex, parse_complex_list, parse_dates, parse_property
-from gis_metadata.utils import update_complex, update_complex_list, update_property
-from gis_metadata.utils import validate_any, validate_complex_list, validate_properties
-from gis_metadata.utils import _complex_definitions, _supported_props, ParserError
+from gis_metadata.utils import update_complex, update_complex_list, update_property, validate_any, validate_properties
+from gis_metadata.utils import _supported_props, ParserError
 
 
 # Place holders for lazy, one-time FGDC & ISO imports
@@ -395,15 +394,6 @@ def validate(self):
         validate_properties(self._data_map, self._metadata_props)
 
         for prop in self._data_map:
-            try:
-                validate_any(prop, getattr(self, prop))
-            except ParserError:
-                if prop in _complex_definitions:
-                    raise  # Enforce basic validation for established structures
-                if prop not in self._data_structures:
-                    raise  # Enforce validation for simple properties
-
-                # Validate custom data structures according to configured structure
-                validate_complex_list(prop, getattr(self, prop), self._data_structures[prop])
+            validate_any(prop, getattr(self, prop), self._data_structures.get(prop))
 
         return self
diff --git a/gis_metadata/tests/tests.py b/gis_metadata/tests/tests.py
index 71d594c..80ae18e 100644
--- a/gis_metadata/tests/tests.py
+++ b/gis_metadata/tests/tests.py
@@ -513,7 +513,6 @@ class MetadataParserTests(MetadataParserTestCase):
     def test_custom_parser(self):
         """ Covers support for custom parsers """
 
-        custom_parser = CustomIsoParser(self.iso_metadata)
         target_values = {
             'metadata_contacts': [{
                 'name': 'Custom Contact Name', 'email': 'Custom Contact Email', 'phone': 'Custom Contact Phone',
@@ -522,6 +521,7 @@ def test_custom_parser(self):
             'metadata_language': 'eng'
         }
 
+        custom_parser = CustomIsoParser(self.iso_metadata)
         for prop in target_values:
             self.assertEqual(getattr(custom_parser, prop), target_values[prop], 'Custom parser values were not parsed')
 
@@ -537,6 +537,26 @@ def test_custom_parser(self):
 
         self.assert_parsers_are_equal(custom_parser, converted_parser)
 
+        # Test invalid custom complex structure value
+
+        metadata_contacts = custom_parser.metadata_contacts
+        custom_parser.metadata_contacts = u'None'
+
+        with self.assertRaises(ParserError):
+            custom_parser.validate()
+
+        custom_parser.metadata_contacts = metadata_contacts
+
+        # Test invalid custom simple value
+
+        metadata_language = custom_parser.metadata_language
+        custom_parser.metadata_language = {}
+
+        with self.assertRaises(ParserError):
+            custom_parser.validate()
+
+        custom_parser.metadata_language = metadata_language
+
     def test_generic_parser(self):
         """ Covers code that enforces certain behaviors for custom parsers """
 
diff --git a/gis_metadata/utils.py b/gis_metadata/utils.py
index 586cfdf..b30490a 100644
--- a/gis_metadata/utils.py
+++ b/gis_metadata/utils.py
@@ -513,9 +513,13 @@ def validate_any(prop, value, xpath_map=None):
         elif prop == PROCESS_STEPS:
             validate_process_steps(prop, value)
 
+        elif prop not in _supported_props and xpath_map is not None:
+            # Validate custom data structures as complex lists by default
+            validate_complex_list(prop, value, xpath_map)
+
         else:
-            for val in wrap_value(value):
-                validate_type(prop, val, string_types)
+            for val in wrap_value(value, include_empty=True):
+                validate_type(prop, val, (string_types, list))
 
 
 def validate_complex(prop, value, xpath_map=None):