diff --git a/docs/releases.md b/docs/releases.md
index 82ae430..ba34c2f 100644
--- a/docs/releases.md
+++ b/docs/releases.md
@@ -1,3 +1,9 @@
+# 0.10.8
+
+## 🐛 Fixes
+
+* Fix populating default values in pk_only child models [#202](https://github.com/collerek/ormar/issues/202)
+
 # 0.10.7
 
 ## ✨ Features
diff --git a/ormar/__init__.py b/ormar/__init__.py
index be40cdd..0540e46 100644
--- a/ormar/__init__.py
+++ b/ormar/__init__.py
@@ -76,7 +76,7 @@ class UndefinedType:  # pragma no cover
 
 Undefined = UndefinedType()
 
-__version__ = "0.10.7"
+__version__ = "0.10.8"
 __all__ = [
     "Integer",
     "BigInteger",
diff --git a/ormar/models/newbasemodel.py b/ormar/models/newbasemodel.py
index f94d0f1..c2a9476 100644
--- a/ormar/models/newbasemodel.py
+++ b/ormar/models/newbasemodel.py
@@ -132,11 +132,15 @@ class NewBaseModel(pydantic.BaseModel, ModelTableProxy, metaclass=ModelMetaclass
 
         new_kwargs, through_tmp_dict = self._process_kwargs(kwargs)
 
-        values, fields_set, validation_error = pydantic.validate_model(
-            self, new_kwargs  # type: ignore
-        )
-        if validation_error and not pk_only:
-            raise validation_error
+        if not pk_only:
+            values, fields_set, validation_error = pydantic.validate_model(
+                self, new_kwargs  # type: ignore
+            )
+            if validation_error:
+                raise validation_error
+        else:
+            fields_set = {self.Meta.pkname}
+            values = new_kwargs
 
         object.__setattr__(self, "__dict__", values)
         object.__setattr__(self, "__fields_set__", fields_set)
diff --git a/tests/test_fastapi/test_relations_with_nested_defaults.py b/tests/test_fastapi/test_relations_with_nested_defaults.py
new file mode 100644
index 0000000..d0d11c8
--- /dev/null
+++ b/tests/test_fastapi/test_relations_with_nested_defaults.py
@@ -0,0 +1,120 @@
+from typing import Optional
+
+import databases
+import pytest
+import sqlalchemy
+from fastapi import FastAPI
+from starlette.testclient import TestClient
+
+import ormar
+from tests.settings import DATABASE_URL
+
+database = databases.Database(DATABASE_URL)
+metadata = sqlalchemy.MetaData()
+
+app = FastAPI()
+app.state.database = database
+
+
+@app.on_event("startup")
+async def startup() -> None:
+    database_ = app.state.database
+    if not database_.is_connected:
+        await database_.connect()
+
+
+@app.on_event("shutdown")
+async def shutdown() -> None:
+    database_ = app.state.database
+    if database_.is_connected:
+        await database_.disconnect()
+
+
+class BaseMeta(ormar.ModelMeta):
+    metadata = metadata
+    database = database
+
+
+class Country(ormar.Model):
+    class Meta(BaseMeta):
+        tablename = "countries"
+
+    id: int = ormar.Integer(primary_key=True)
+    name: str = ormar.String(max_length=100, default="Poland")
+
+
+class Author(ormar.Model):
+    class Meta(BaseMeta):
+        tablename = "authors"
+
+    id: int = ormar.Integer(primary_key=True)
+    name: str = ormar.String(max_length=100)
+    rating: int = ormar.Integer(default=0)
+    country: Optional[Country] = ormar.ForeignKey(Country)
+
+
+class Book(ormar.Model):
+    class Meta(BaseMeta):
+        tablename = "books"
+
+    id: int = ormar.Integer(primary_key=True)
+    author: Optional[Author] = ormar.ForeignKey(Author)
+    title: str = ormar.String(max_length=100)
+    year: int = ormar.Integer(nullable=True)
+
+
+@pytest.fixture(autouse=True, scope="module")
+def create_test_database():
+    engine = sqlalchemy.create_engine(DATABASE_URL)
+    metadata.create_all(engine)
+    yield
+    metadata.drop_all(engine)
+
+
+@pytest.fixture()
+async def sample_data():
+    country = await Country(id=1, name="USA").save()
+    author = await Author(id=1, name="bug", rating=5, country=country).save()
+    await Book(
+        id=1, author=author, title="Bug caused by default value", year=2021
+    ).save()
+
+
+@app.get("/books/{book_id}", response_model=Book)
+async def get_book_by_id(book_id: int):
+    book = await Book.objects.get(id=book_id)
+    return book
+
+
+@app.get("/books_with_author/{book_id}", response_model=Book)
+async def get_book_with_author_by_id(book_id: int):
+    book = await Book.objects.select_related("author").get(id=book_id)
+    return book
+
+
+def test_related_with_defaults(sample_data):
+    client = TestClient(app)
+    with client as client:
+        response = client.get("/books/1")
+        assert response.json() == {
+            "author": {"id": 1},
+            "id": 1,
+            "title": "Bug caused by default value",
+            "year": 2021,
+        }
+
+        response = client.get("/books_with_author/1")
+        assert response.json() == {
+            "author": {
+                "books": [
+                    {"id": 1, "title": "Bug caused by default value", "year": 2021}
+                ],
+                "country": {"id": 1},
+                "id": 1,
+                "name": "bug",
+                "rating": 5,
+            },
+            "id": 1,
+            "title": "Bug caused by default value",
+            "year": 2021,
+        }