diff --git a/tests/fixtures/defxmlschema/chapter08/chapter08.py b/tests/fixtures/defxmlschema/chapter08/chapter08.py
index 484be3320..82d61cef6 100644
--- a/tests/fixtures/defxmlschema/chapter08/chapter08.py
+++ b/tests/fixtures/defxmlschema/chapter08/chapter08.py
@@ -1,6 +1,6 @@
 from enum import Enum
 from dataclasses import dataclass, field
-from typing import List, Union
+from typing import List
 
 
 class SmlxsizeType(Enum):
@@ -16,6 +16,21 @@ class SmlxsizeType(Enum):
     EXTRA_LARGE = "extra large"
 
 
+class XsmlxsizeType(Enum):
+    """
+    :cvar SMALL:
+    :cvar MEDIUM:
+    :cvar LARGE:
+    :cvar EXTRA_LARGE:
+    :cvar EXTRA_SMALL:
+    """
+    SMALL = "small"
+    MEDIUM = "medium"
+    LARGE = "large"
+    EXTRA_LARGE = "extra large"
+    EXTRA_SMALL = "extra small"
+
+
 @dataclass
 class SizesType:
     """
@@ -74,7 +89,7 @@ class SizesType:
             max_occurs=9223372036854775807
         )
     )
-    xsmlx_size: List[Union[SmlxsizeType, "SizesType.Value"]] = field(
+    xsmlx_size: List[XsmlxsizeType] = field(
         default_factory=list,
         metadata=dict(
             name="xsmlxSize",
@@ -85,12 +100,6 @@ class SizesType:
         )
     )
 
-    class Value(Enum):
-        """
-        :cvar EXTRA_SMALL:
-        """
-        EXTRA_SMALL = "extra small"
-
 
 @dataclass
 class Sizes(SizesType):
diff --git a/tests/fixtures/defxmlschema/chapter08/example0812.py b/tests/fixtures/defxmlschema/chapter08/example0812.py
index 67aa0d18c..34e8c1053 100644
--- a/tests/fixtures/defxmlschema/chapter08/example0812.py
+++ b/tests/fixtures/defxmlschema/chapter08/example0812.py
@@ -1,25 +1,16 @@
 from enum import Enum
-from dataclasses import dataclass, field
-from typing import Optional, Union
-from tests.fixtures.defxmlschema.chapter08.example0809 import (
-    SmlxsizeType,
-)
 
 
-@dataclass
-class XsmlxsizeType:
+class XsmlxsizeType(Enum):
     """
-    :ivar value:
+    :cvar SMALL:
+    :cvar MEDIUM:
+    :cvar LARGE:
+    :cvar EXTRA_LARGE:
+    :cvar EXTRA_SMALL:
     """
-    class Meta:
-        name = "XSMLXSizeType"
-
-    value: Optional[Union[SmlxsizeType, "XsmlxsizeType.Value"]] = field(
-        default=None,
-    )
-
-    class Value(Enum):
-        """
-        :cvar EXTRA_SMALL:
-        """
-        EXTRA_SMALL = "extra small"
+    SMALL = "small"
+    MEDIUM = "medium"
+    LARGE = "large"
+    EXTRA_LARGE = "extra large"
+    EXTRA_SMALL = "extra small"
diff --git a/tests/fixtures/defxmlschema/chapter10/example1010.py b/tests/fixtures/defxmlschema/chapter10/example1010.py
index cfe41de26..f72582dbe 100644
--- a/tests/fixtures/defxmlschema/chapter10/example1010.py
+++ b/tests/fixtures/defxmlschema/chapter10/example1010.py
@@ -1,19 +1,14 @@
-from dataclasses import dataclass, field
-from typing import List
-from tests.fixtures.defxmlschema.chapter08.example0810 import (
-    SmlsizeType,
-)
+from enum import Enum
 
 
-@dataclass
-class AvailableSizesType:
+class AvailableSizesType(Enum):
     """
-    :ivar value:
+    :cvar SMALL:
+    :cvar MEDIUM:
+    :cvar LARGE:
+    :cvar EXTRA_LARGE:
     """
-    value: List[SmlsizeType] = field(
-        default_factory=list,
-        metadata=dict(
-            min_occurs=0,
-            max_occurs=9223372036854775807
-        )
-    )
+    SMALL = "small"
+    MEDIUM = "medium"
+    LARGE = "large"
+    EXTRA_LARGE = "extra large"
diff --git a/tests/fixtures/defxmlschema/chapter10/example1013.py b/tests/fixtures/defxmlschema/chapter10/example1013.py
index 9c222a053..0899c3fef 100644
--- a/tests/fixtures/defxmlschema/chapter10/example1013.py
+++ b/tests/fixtures/defxmlschema/chapter10/example1013.py
@@ -1,27 +1,12 @@
 from enum import Enum
-from dataclasses import dataclass, field
-from typing import List
 
 
-@dataclass
-class AvailableSizesType:
+class AvailableSizesType(Enum):
     """
-    :ivar value:
+    :cvar SMALL:
+    :cvar MEDIUM:
+    :cvar LARGE:
     """
-    value: List["AvailableSizesType.Value"] = field(
-        default_factory=list,
-        metadata=dict(
-            min_occurs=0,
-            max_occurs=9223372036854775807
-        )
-    )
-
-    class Value(Enum):
-        """
-        :cvar SMALL:
-        :cvar MEDIUM:
-        :cvar LARGE:
-        """
-        SMALL = "small"
-        MEDIUM = "medium"
-        LARGE = "large"
+    SMALL = "small"
+    MEDIUM = "medium"
+    LARGE = "large"
diff --git a/tests/fixtures/defxmlschema/chapter10/example1016.py b/tests/fixtures/defxmlschema/chapter10/example1016.py
index c6e51a7ab..f918c1a6e 100644
--- a/tests/fixtures/defxmlschema/chapter10/example1016.py
+++ b/tests/fixtures/defxmlschema/chapter10/example1016.py
@@ -1,9 +1,7 @@
 from enum import Enum
-from dataclasses import dataclass, field
-from typing import List
 
 
-class SmlxsizeType(Enum):
+class AvailableSizesType(Enum):
     """
     :cvar SMALL:
     :cvar MEDIUM:
@@ -16,15 +14,14 @@ class SmlxsizeType(Enum):
     EXTRA_LARGE = "extra large"
 
 
-@dataclass
-class AvailableSizesType:
+class SmlxsizeType(Enum):
     """
-    :ivar value:
+    :cvar SMALL:
+    :cvar MEDIUM:
+    :cvar LARGE:
+    :cvar EXTRA_LARGE:
     """
-    value: List[SmlxsizeType] = field(
-        default_factory=list,
-        metadata=dict(
-            min_occurs=0,
-            max_occurs=9223372036854775807
-        )
-    )
+    SMALL = "small"
+    MEDIUM = "medium"
+    LARGE = "large"
+    EXTRA_LARGE = "extra large"
diff --git a/tests/test_analyzer.py b/tests/test_analyzer.py
index 173bf633d..0b0683417 100644
--- a/tests/test_analyzer.py
+++ b/tests/test_analyzer.py
@@ -239,12 +239,14 @@ def test_find_simple_class(self):
     @mock.patch.object(ClassAnalyzer, "create_mixed_attribute")
     @mock.patch.object(ClassAnalyzer, "add_substitution_attrs")
     @mock.patch.object(ClassAnalyzer, "flatten_attribute_types")
+    @mock.patch.object(ClassAnalyzer, "flatten_enumeration_unions")
     @mock.patch.object(ClassAnalyzer, "flatten_extension")
     @mock.patch.object(ClassAnalyzer, "expand_attribute_group")
     def test_flatten_class(
         self,
         mock_expand_attribute_group,
         mock_flatten_extension,
+        mock_flatten_enumeration_unions,
         mock_flatten_attribute_types,
         mock_add_substitution_attrs,
         mock_create_mixed_attribute,
@@ -267,6 +269,10 @@ def test_flatten_class(
             ]
         )
 
+        mock_flatten_enumeration_unions.assert_has_calls(
+            [mock.call(target), mock.call(target.inner[0]),]
+        )
+
         mock_flatten_attribute_types.assert_has_calls(
             [mock.call(target, target.attrs[0]), mock.call(target, target.attrs[1])]
         )
@@ -557,6 +563,48 @@ def test_expand_attribute_group_with_unknown_source(self):
 
         self.assertEqual("Group attribute not found: `{foo}bar`", str(cm.exception))
 
+    def test_flatten_enumeration_unions(self):
+        root_enum = ClassFactory.enumeration(2)
+        inner_enum = ClassFactory.enumeration(2)
+        target = ClassFactory.create(
+            type=Element,
+            attrs=[
+                AttrFactory.create(
+                    name="value",
+                    types=[
+                        AttrTypeFactory.create(name=root_enum.name),
+                        AttrTypeFactory.create(name=inner_enum.name, forward_ref=True),
+                        AttrTypeFactory.xs_int(),
+                    ],
+                ),
+                AttrFactory.create(),
+            ],
+        )
+        target.inner.append(inner_enum)
+        self.analyzer.create_class_index([root_enum, target])
+
+        # Target has more than one attribute
+        self.analyzer.flatten_enumeration_unions(target)
+        self.assertFalse(target.is_enumeration)
+
+        # Target has one attribute but is not a simple type
+        target.attrs.pop()
+        self.analyzer.flatten_enumeration_unions(target)
+        self.assertFalse(target.is_enumeration)
+
+        # Attribute is not a union of enumerations only
+        target.type = SimpleType
+        self.analyzer.flatten_enumeration_unions(target)
+        self.assertFalse(target.is_enumeration)
+
+        # Winner: single attr named with a union of enum types
+        target.attrs[0].types.pop()
+        self.analyzer.flatten_enumeration_unions(target)
+        self.assertTrue(target.is_enumeration)
+
+        self.assertEqual(root_enum.attrs + inner_enum.attrs, target.attrs)
+        self.assertEqual(0, len(target.inner))
+
     def test_flatten_attribute_types_when_type_is_native(self):
         xs_bool = AttrTypeFactory.xs_bool()
         xs_decimal = AttrTypeFactory.xs_decimal()
diff --git a/xsdata/analyzer.py b/xsdata/analyzer.py
index 74434ebd6..5761d5a0f 100644
--- a/xsdata/analyzer.py
+++ b/xsdata/analyzer.py
@@ -1,6 +1,7 @@
 from collections import defaultdict
 from dataclasses import dataclass
 from dataclasses import field
+from typing import Any
 from typing import Callable
 from typing import Dict
 from typing import List
@@ -202,6 +203,8 @@ def flatten_class(self, target: Class):
         for extension in reversed(target.extensions):
             self.flatten_extension(target, extension)
 
+        self.flatten_enumeration_unions(target)
+
         for attr in list(target.attrs):
             self.flatten_attribute_types(target, attr)
 
@@ -216,6 +219,27 @@ def flatten_class(self, target: Class):
             if id(inner) not in self.processed:
                 self.flatten_class(inner)
 
+    def flatten_enumeration_unions(self, target: Class):
+        """Convert simple types with a single field which is a union of enums
+        to a standalone enumeration."""
+        if len(target.attrs) == 1 and target.is_simple:
+            enums: List[Any] = list()
+            attr = target.attrs[0]
+            for attr_type in attr.types:
+                if attr_type.forward_ref:
+                    enums.extend(target.inner)
+                elif not attr_type.native:
+                    enums.append(self.find_attr_type(target, attr_type))
+                else:
+                    enums.append(None)
+
+            merge = all(isinstance(x, Class) and x.is_enumeration for x in enums)
+            if merge:
+                target.attrs.clear()
+                target.inner.clear()
+                for enum in enums:
+                    target.attrs.extend(enum.attrs)
+
     def flatten_extension(self, target: Class, extension: Extension):
         """
         Flatten target class extension based on the extension type.