diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 669a90031..76f956472 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -11,7 +11,7 @@ repos:
     hooks:
       - id: reorder-python-imports
   - repo: https://github.com/ambv/black
-    rev: 22.6.0
+    rev: 22.8.0
     hooks:
       - id: black
   - repo: https://gitlab.com/pycqa/flake8
diff --git a/tests/codegen/handlers/test_flatten_attribute_groups.py b/tests/codegen/handlers/test_flatten_attribute_groups.py
index 1655f5049..3a4f66f8a 100644
--- a/tests/codegen/handlers/test_flatten_attribute_groups.py
+++ b/tests/codegen/handlers/test_flatten_attribute_groups.py
@@ -47,7 +47,7 @@ def test_process(self, mock_process_attribute, mock_is_group):
     @mock.patch.object(ClassUtils, "copy_group_attributes")
     def test_process_attribute_with_group(self, mock_copy_group_attributes):
         complex_bar = ClassFactory.create(qname="bar", tag=Tag.COMPLEX_TYPE)
-        group_bar = ClassFactory.create(qname="bar", tag=Tag.GROUP)
+        group_bar = ClassFactory.create(qname="bar", tag=Tag.ATTRIBUTE_GROUP)
         group_attr = AttrFactory.attribute_group(name="bar")
         target = ClassFactory.create()
         target.attrs.append(group_attr)
@@ -80,7 +80,7 @@ def test_process_attribute_with_attribute_group(self, mock_copy_group_attributes
 
     def test_process_attribute_with_circular_reference(self):
         group_attr = AttrFactory.attribute_group(name="bar")
-        target = ClassFactory.create(qname="bar", tag=Tag.GROUP)
+        target = ClassFactory.create(qname="bar", tag=Tag.ATTRIBUTE_GROUP)
         target.attrs.append(group_attr)
 
         target.status = Status.FLATTENING
diff --git a/xsdata/codegen/handlers/flatten_attribute_groups.py b/xsdata/codegen/handlers/flatten_attribute_groups.py
index e2e23787a..67f2fa6ac 100644
--- a/xsdata/codegen/handlers/flatten_attribute_groups.py
+++ b/xsdata/codegen/handlers/flatten_attribute_groups.py
@@ -1,13 +1,12 @@
 from xsdata.codegen.mixins import RelativeHandlerInterface
 from xsdata.codegen.models import Attr
 from xsdata.codegen.models import Class
-from xsdata.codegen.models import is_group
 from xsdata.codegen.utils import ClassUtils
 from xsdata.exceptions import AnalyzerValueError
 
 
 class FlattenAttributeGroups(RelativeHandlerInterface):
-    """Replace attribute groups with the source class attributes."""
+    """Replace groups and attGroups with the source class attributes."""
 
     __slots__ = ()
 
@@ -36,7 +35,7 @@ def process_attribute(self, target: Class, attr: Attr):
         :raises AnalyzerValueError: if source class is not found.
         """
         qname = attr.types[0].qname  # group attributes have one type only.
-        source = self.container.find(qname, condition=is_group)
+        source = self.container.find(qname, condition=lambda x: x.tag == attr.tag)
 
         if not source:
             raise AnalyzerValueError(f"Group attribute not found: `{qname}`")