diff --git a/openapi_python_client/parser/properties/__init__.py b/openapi_python_client/parser/properties/__init__.py
index 2ea75a569..992d726df 100644
--- a/openapi_python_client/parser/properties/__init__.py
+++ b/openapi_python_client/parser/properties/__init__.py
@@ -302,6 +302,12 @@ def build_model_property(
         name=name,
         additional_properties=additional_properties,
     )
+    if prop.reference.class_name in schemas.models:
+        error = PropertyError(
+            data=data, detail=f'Attempted to generate duplicate models with name "{prop.reference.class_name}"'
+        )
+        return error, schemas
+
     schemas = attr.evolve(schemas, models={**schemas.models, prop.reference.class_name: prop})
     return prop, schemas
 
diff --git a/tests/test_parser/test_properties/test_init.py b/tests/test_parser/test_properties/test_init.py
index a7ea05881..ee07d3973 100644
--- a/tests/test_parser/test_properties/test_init.py
+++ b/tests/test_parser/test_properties/test_init.py
@@ -1105,6 +1105,31 @@ def test_build_model_property(additional_properties_schema, expected_additional_
     )
 
 
+def test_build_model_property_conflict():
+    from openapi_python_client.parser.properties import Schemas, build_model_property
+
+    data = oai.Schema.construct(
+        required=["req"],
+        properties={
+            "req": oai.Schema.construct(type="string"),
+            "opt": oai.Schema(type="string", format="date-time"),
+        },
+        nullable=False,
+    )
+    schemas = Schemas(models={"OtherModel": None})
+
+    err, new_schemas = build_model_property(
+        data=data,
+        name="OtherModel",
+        schemas=schemas,
+        required=True,
+        parent_name=None,
+    )
+
+    assert new_schemas == schemas
+    assert err == PropertyError(detail='Attempted to generate duplicate models with name "OtherModel"', data=data)
+
+
 def test_build_model_property_bad_prop():
     from openapi_python_client.parser.properties import Schemas, build_model_property