diff --git a/docs/releases.md b/docs/releases.md
index ac31dff..a09424b 100644
--- a/docs/releases.md
+++ b/docs/releases.md
@@ -1,3 +1,7 @@
+# 0.7.2
+
+* Fix for overwriting related models with pk only in `Model.update() with fields passed as parameters` (fix [#70][#70])
+
 # 0.7.1
 
 * Fix for overwriting related models with pk only in `Model.save()` (fix [#68][#68])
@@ -183,4 +187,5 @@ Add queryset level methods
 
 [#19]: https://github.com/collerek/ormar/issues/19
 [#60]: https://github.com/collerek/ormar/issues/60
-[#68]: https://github.com/collerek/ormar/issues/68
\ No newline at end of file
+[#68]: https://github.com/collerek/ormar/issues/68
+[#70]: https://github.com/collerek/ormar/issues/70
\ No newline at end of file
diff --git a/ormar/__init__.py b/ormar/__init__.py
index 173c4f5..0319847 100644
--- a/ormar/__init__.py
+++ b/ormar/__init__.py
@@ -44,7 +44,7 @@ class UndefinedType:  # pragma no cover
 
 Undefined = UndefinedType()
 
-__version__ = "0.7.1"
+__version__ = "0.7.2"
 __all__ = [
     "Integer",
     "BigInteger",
diff --git a/ormar/models/model.py b/ormar/models/model.py
index d412a89..8e7a8f5 100644
--- a/ormar/models/model.py
+++ b/ormar/models/model.py
@@ -269,8 +269,7 @@ class Model(NewBaseModel):
 
     async def update(self: T, **kwargs: Any) -> T:
         if kwargs:
-            new_values = {**self.dict(), **kwargs}
-            self.from_dict(new_values)
+            self.from_dict(kwargs)
 
         if not self.pk:
             raise ModelPersistenceError(
diff --git a/tests/test_saving_nullable_fields.py b/tests/test_saving_nullable_fields.py
new file mode 100644
index 0000000..cc8eb36
--- /dev/null
+++ b/tests/test_saving_nullable_fields.py
@@ -0,0 +1,67 @@
+from typing import Optional
+
+import databases
+import sqlalchemy
+from sqlalchemy import create_engine
+
+import ormar
+import pytest
+
+from tests.settings import DATABASE_URL
+
+db = databases.Database(DATABASE_URL, force_rollback=True)
+metadata = sqlalchemy.MetaData()
+
+
+class PrimaryModel(ormar.Model):
+    class Meta:
+        metadata = metadata
+        database = db
+        tablename = "primary_models"
+
+    id: int = ormar.Integer(primary_key=True)
+    name: str = ormar.String(max_length=255, index=True)
+    some_text: str = ormar.Text()
+    # NOTE: Removing nullable=True makes the test pass.
+    some_other_text: Optional[str] = ormar.Text(nullable=True)
+
+
+class SecondaryModel(ormar.Model):
+    class Meta:
+        metadata = metadata
+        database = db
+        tablename = "secondary_models"
+
+    id: int = ormar.Integer(primary_key=True)
+    name: str = ormar.String(max_length=100)
+    primary_model: PrimaryModel = ormar.ForeignKey(
+        PrimaryModel, related_name="secondary_models",
+    )
+
+
+@pytest.fixture(autouse=True, scope="module")
+def create_test_database():
+    engine = create_engine(DATABASE_URL)
+    metadata.create_all(engine)
+    yield
+    metadata.drop_all(engine)
+
+
+@pytest.mark.asyncio
+async def test_create_models():
+    primary = await PrimaryModel(
+        name="Foo", some_text="Bar", some_other_text="Baz"
+    ).save()
+    assert primary.id == 1
+
+    secondary = await SecondaryModel(name="Foo", primary_model=primary).save()
+    assert secondary.id == 1
+    assert secondary.primary_model.id == 1
+
+
+@pytest.mark.asyncio
+async def test_update_secondary():
+    secondary = await SecondaryModel.objects.get(id=1)
+    assert secondary.name == "Foo"
+    await secondary.update(name="Updated")
+    assert secondary.name == "Updated"
diff --git a/tests/test_saving_related.py b/tests/test_saving_related.py
index 26c7000..6dd4fd2 100644
--- a/tests/test_saving_related.py
+++ b/tests/test_saving_related.py
@@ -55,7 +55,7 @@ async def test_model_relationship():
             assert ws.topic == "Topic 1"
             assert ws.category.name == "Foo"
 
-            ws.topic = 'Topic 2'
+            ws.topic = "Topic 2"
             await ws.update()
 
             assert ws.id == 1