diff --git a/tests/validators/test_models.py b/tests/validators/test_models.py
index 47a6893f..744f94c2 100644
--- a/tests/validators/test_models.py
+++ b/tests/validators/test_models.py
@@ -11,6 +11,7 @@
 """Tests concerning model groups validation"""
 import unittest
 import os.path
+import warnings
 from textwrap import dedent
 from typing import Any, Union, List, Optional
 
@@ -1076,22 +1077,12 @@ def test_iter_collapsed_content_with_optional_elements(self):
             """)
 
         group = schema.types['A_type'].content
-        model = ModelVisitor(group)
-
         content = [('B3', 10), ('B4', None), ('B5', True), ('B6', 'alpha'), ('B7', 20)]
-        model.restart()
-        self.assertListEqual(
-            list(model.iter_collapsed_content(content)), content
-        )
         self.assertListEqual(
             list(iter_collapsed_content(content, group)), content
         )
 
         content = [('B3', 10), ('B5', True), ('B6', 'alpha'), ('B7', 20)]  # Missing B4
-        model.restart()
-        self.assertListEqual(
-            list(model.iter_collapsed_content(content)), content
-        )
         self.assertListEqual(
             list(iter_collapsed_content(content, group)), content
         )
@@ -1202,6 +1193,64 @@ def test_iter_collapsed_content_with_single_elements(self):
         content = [('X', None), ('B1', 'abc'), ('B2', 10), ('B3', False)]
         self.assertListEqual(list(iter_collapsed_content(content, group)), content)
 
+    def test_deprecated_methods(self):
+        schema = self.get_schema("""
+            <xs:element name="A" type="A_type" />
+            <xs:complexType name="A_type">
+                <xs:sequence maxOccurs="10">
+                    <xs:element name="B1" minOccurs="0" />
+                    <xs:element name="B2" minOccurs="0" />
+                </xs:sequence>
+            </xs:complexType>
+            """)
+
+        group = schema.types['A_type'].content
+        model = ModelVisitor(group)
+        default_namespace = 'http://xmlschema.test/ns'
+        content = [('B1', 1), ('B1', 2), ('B2', 3)]
+
+        with warnings.catch_warnings(record=True) as ctx:
+            warnings.   simplefilter("always")
+            self.assertListEqual(
+                list(model.iter_collapsed_content(content)),
+                [('B1', 1), ('B2', 3), ('B1', 2)]
+            )
+            self.assertEqual(len(ctx), 1, "Expected one deprecation warning")
+            self.assertIn("use iter_collapsed_content()", str(ctx[0].message))
+            self.assertNotIn("Don't provide default_namespace", str(ctx[0].message))
+
+        with warnings.catch_warnings(record=True) as ctx:
+            warnings.simplefilter("always")
+            self.assertListEqual(
+                list(model.iter_collapsed_content(content, default_namespace)),
+                [('B1', 1), ('B2', 3), ('B1', 2)]
+            )
+            self.assertEqual(len(ctx), 1, "Expected one deprecation warning")
+            self.assertIn("use iter_collapsed_content()", str(ctx[0].message))
+            self.assertIn("Don't provide default_namespace", str(ctx[0].message))
+
+        content = [('B2', 1), ('B1', 2), ('B2', 3), ('B1', 4)]
+
+        with warnings.catch_warnings(record=True) as ctx:
+            warnings.   simplefilter("always")
+            self.assertListEqual(
+                list(model.iter_unordered_content(content)),
+                [('B1', 2), ('B2', 1), ('B1', 4), ('B2', 3)]
+            )
+            self.assertEqual(len(ctx), 1, "Expected one deprecation warning")
+            self.assertIn("use iter_unordered_content()", str(ctx[0].message))
+            self.assertNotIn("Don't provide default_namespace", str(ctx[0].message))
+
+        with warnings.catch_warnings(record=True) as ctx:
+            warnings.simplefilter("always")
+            self.assertListEqual(
+                list(model.iter_unordered_content(content, default_namespace)),
+                [('B1', 2), ('B2', 1), ('B1', 4), ('B2', 3)]
+            )
+            self.assertEqual(len(ctx), 1, "Expected one deprecation warning")
+            self.assertIn("use iter_unordered_content()", str(ctx[0].message))
+            self.assertIn("Don't provide default_namespace", str(ctx[0].message))
+
 
 class TestModelPaths(unittest.TestCase):
 
diff --git a/xmlschema/validators/groups.py b/xmlschema/validators/groups.py
index b17c4d5c..d762bcc3 100644
--- a/xmlschema/validators/groups.py
+++ b/xmlschema/validators/groups.py
@@ -1137,7 +1137,7 @@ def iter_encode(self, obj: ElementData, validation: str = 'lax', **kwargs: Any)
         if not obj.content:
             content = []
         elif isinstance(obj.content, MutableMapping) or kwargs.get('unordered'):
-            content = iter_unordered_content(obj.content, self, default_namespace)
+            content = iter_unordered_content(obj.content, self)
         elif not isinstance(obj.content, MutableSequence):
             wrong_content_type = True
             content = []
@@ -1150,7 +1150,7 @@ def iter_encode(self, obj: ElementData, validation: str = 'lax', **kwargs: Any)
         elif converter.losslessly:
             content = obj.content
         else:
-            content = iter_collapsed_content(obj.content, self, default_namespace)
+            content = iter_collapsed_content(obj.content, self)
 
         for index, (name, value) in enumerate(content):
             if isinstance(name, int):
diff --git a/xmlschema/validators/models.py b/xmlschema/validators/models.py
index 4fbe4d58..b96f6f1a 100644
--- a/xmlschema/validators/models.py
+++ b/xmlschema/validators/models.py
@@ -15,6 +15,7 @@
 from operator import attrgetter
 from typing import Any, Dict, Iterable, Iterator, List, \
     MutableMapping, MutableSequence, Optional, Tuple, Union
+import warnings
 
 from ..exceptions import XMLSchemaValueError
 from ..aliases import ModelGroupType, ModelParticleType, SchemaElementType, \
@@ -465,12 +466,26 @@ def _iter_all_model_errors(self, occurs: OccursCounterType) -> Iterator[AdvanceY
     def iter_unordered_content(
             self, content: EncodedContentType,
             default_namespace: Optional[str] = None) -> Iterator[ContentItemType]:
-        return iter_unordered_content(content, self.root, default_namespace)
+
+        msg = f"{self.__class__.__name__}.iter_unordered_content() method will " \
+              "be removed in v4.0, use iter_unordered_content() function instead."
+        if default_namespace is not None:
+            msg += " Don't provide default_namespace argument, it's ignored."
+        warnings.warn(msg, DeprecationWarning, stacklevel=2)
+
+        return iter_unordered_content(content, self.root)
 
     def iter_collapsed_content(
             self, content: Iterable[ContentItemType],
             default_namespace: Optional[str] = None) -> Iterator[ContentItemType]:
-        return iter_collapsed_content(content, self.root, default_namespace)
+
+        msg = f"{self.__class__.__name__}.iter_collapsed_content() method will " \
+              "be removed in v4.0, use iter_collapsed_content() function instead."
+        if default_namespace is not None:
+            msg += " Don't provide default_namespace argument, it's ignored."
+        warnings.warn(msg, DeprecationWarning, stacklevel=2)
+
+        return iter_collapsed_content(content, self.root)
 
 
 class InterleavedModelVisitor(ModelVisitor):
@@ -555,10 +570,8 @@ def advance(self, match: bool = False) -> Iterator[AdvanceYieldedType]:
 #
 # Functions for manipulating encoded content
 
-def iter_unordered_content(
-        content: EncodedContentType,
-        group: ModelGroupType,
-        default_namespace: Optional[str] = None) -> Iterator[ContentItemType]:
+def iter_unordered_content(content: EncodedContentType, group: ModelGroupType) \
+        -> Iterator[ContentItemType]:
     """
     Takes an unordered content stored in a dictionary of lists and yields the
     content elements sorted with the ordering defined by the model group. Character
@@ -574,7 +587,6 @@ def iter_unordered_content(
     dictionary the values must be lists where each item is the content \
     of a single element.
     :param group: the model group related to content.
-    :param default_namespace: the default namespace to apply for matching names.
     """
     consumable_content: Dict[str, Any]
 
@@ -624,16 +636,13 @@ def iter_unordered_content(
         yield cdata_content.pop()
 
 
-def sort_content(content: EncodedContentType,
-                 group: ModelGroupType,
-                 default_namespace: Optional[str] = None) -> List[ContentItemType]:
-    return [x for x in iter_unordered_content(content, group, default_namespace)]
+def sort_content(content: EncodedContentType, group: ModelGroupType) \
+        -> List[ContentItemType]:
+    return [x for x in iter_unordered_content(content, group)]
 
 
-def iter_collapsed_content(
-        content: Iterable[ContentItemType],
-        group: ModelGroupType,
-        default_namespace: Optional[str] = None) -> Iterator[ContentItemType]:
+def iter_collapsed_content(content: Iterable[ContentItemType], group: ModelGroupType) \
+        -> Iterator[ContentItemType]:
     """
     Iterates a content stored in a sequence of couples *(name, value)*, yielding
     items in the same order of the sequence, except for repetitions of the same
@@ -647,7 +656,6 @@ def iter_collapsed_content(
 
     :param content: an iterable containing couples of names and values.
     :param group: the model group related to content.
-    :param default_namespace: the default namespace to apply for matching names.
     """
     prev_name = None
     unordered_content: Dict[str, Any] = defaultdict(deque)
@@ -689,7 +697,7 @@ def iter_collapsed_content(
             yield name, value
             prev_name = name
 
-    # Add the remaining consumable content onto the end of the data.
+    # Yields the remaining consumable content after the end of the data.
     for name, values in unordered_content.items():
         for v in values:
             yield name, v