diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 08b22ce399e..6070168905d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -246,9 +246,6 @@ jobs:
       with:
         python-version: '3.10'
 
-    - name: upgrade pip
-      run: pip install -U pip setuptools wheel
-
     - name: install
       run: make install-testing
 
diff --git a/changes/3641-PrettyWood.md b/changes/3641-PrettyWood.md
new file mode 100644
index 00000000000..d0338c66369
--- /dev/null
+++ b/changes/3641-PrettyWood.md
@@ -0,0 +1 @@
+`Config.copy_on_model_validation` does a deep copy and not a shallow one
\ No newline at end of file
diff --git a/pydantic/main.py b/pydantic/main.py
index eea8abcbbe8..1dcda9efd55 100644
--- a/pydantic/main.py
+++ b/pydantic/main.py
@@ -666,7 +666,7 @@ def __get_validators__(cls) -> 'CallableGenerator':
     def validate(cls: Type['Model'], value: Any) -> 'Model':
         if isinstance(value, cls):
             if cls.__config__.copy_on_model_validation:
-                return value._copy_and_set_values(value.__dict__, value.__fields_set__, deep=False)
+                return value._copy_and_set_values(value.__dict__, value.__fields_set__, deep=True)
             else:
                 return value
 
diff --git a/tests/test_main.py b/tests/test_main.py
index c00d70688cb..f4d3844c4aa 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -1561,12 +1561,28 @@ class Config:
 
     assert t.user is not my_user
     assert t.user.hobbies == ['scuba diving']
-    assert t.user.hobbies is my_user.hobbies  # `Config.copy_on_model_validation` only does a shallow copy
+    assert t.user.hobbies is not my_user.hobbies  # `Config.copy_on_model_validation` does a deep copy
     assert t.user._priv == 13
     assert t.user.password.get_secret_value() == 'hashedpassword'
     assert t.dict() == {'id': '1234567890', 'user': {'id': 42, 'hobbies': ['scuba diving']}}
 
 
+def test_validation_deep_copy():
+    """By default, Config.copy_on_model_validation should do a deep copy"""
+
+    class A(BaseModel):
+        name: str
+
+    class B(BaseModel):
+        list_a: List[A]
+
+    a = A(name='a')
+    b = B(list_a=[a])
+    assert b.list_a == [A(name='a')]
+    a.name = 'b'
+    assert b.list_a == [A(name='a')]
+
+
 @pytest.mark.parametrize(
     'kinds',
     [