diff --git a/rest_framework/fields.py b/rest_framework/fields.py
index 8c80d6bd5a..11a2915683 100644
--- a/rest_framework/fields.py
+++ b/rest_framework/fields.py
@@ -30,7 +30,7 @@
 from django.utils.translation import gettext_lazy as _
 from pytz.exceptions import InvalidTimeError
 
-from rest_framework import ISO_8601
+from rest_framework import ISO_8601, RemovedInDRF313Warning
 from rest_framework.compat import ProhibitNullCharactersValidator
 from rest_framework.exceptions import ErrorDetail, ValidationError
 from rest_framework.settings import api_settings
@@ -263,10 +263,10 @@ def __call__(self, serializer_field):
             if hasattr(self.default, 'set_context'):
                 warnings.warn(
                     "Method `set_context` on defaults is deprecated and will "
-                    "no longer be called starting with 3.12. Instead set "
+                    "no longer be called starting with 3.13. Instead set "
                     "`requires_context = True` on the class, and accept the "
                     "context as an additional argument.",
-                    DeprecationWarning, stacklevel=2
+                    RemovedInDRF313Warning, stacklevel=2
                 )
                 self.default.set_context(self)
 
@@ -502,10 +502,10 @@ def get_default(self):
             if hasattr(self.default, 'set_context'):
                 warnings.warn(
                     "Method `set_context` on defaults is deprecated and will "
-                    "no longer be called starting with 3.12. Instead set "
+                    "no longer be called starting with 3.13. Instead set "
                     "`requires_context = True` on the class, and accept the "
                     "context as an additional argument.",
-                    DeprecationWarning, stacklevel=2
+                    RemovedInDRF313Warning, stacklevel=2
                 )
                 self.default.set_context(self)
 
@@ -576,10 +576,10 @@ def run_validators(self, value):
             if hasattr(validator, 'set_context'):
                 warnings.warn(
                     "Method `set_context` on validators is deprecated and will "
-                    "no longer be called starting with 3.12. Instead set "
+                    "no longer be called starting with 3.13. Instead set "
                     "`requires_context = True` on the class, and accept the "
                     "context as an additional argument.",
-                    DeprecationWarning, stacklevel=2
+                    RemovedInDRF313Warning, stacklevel=2
                 )
                 validator.set_context(self)
 
diff --git a/rest_framework/validators.py b/rest_framework/validators.py
index 2907312a9b..aa79377142 100644
--- a/rest_framework/validators.py
+++ b/rest_framework/validators.py
@@ -41,7 +41,6 @@ class UniqueValidator:
 
     def __init__(self, queryset, message=None, lookup='exact'):
         self.queryset = queryset
-        self.serializer_field = None
         self.message = message or self.message
         self.lookup = lookup
 
@@ -94,15 +93,14 @@ class UniqueTogetherValidator:
     def __init__(self, queryset, fields, message=None):
         self.queryset = queryset
         self.fields = fields
-        self.serializer_field = None
         self.message = message or self.message
 
-    def enforce_required_fields(self, attrs, instance):
+    def enforce_required_fields(self, attrs, serializer):
         """
         The `UniqueTogetherValidator` always forces an implied 'required'
         state on the fields it applies to.
         """
-        if instance is not None:
+        if serializer.instance is not None:
             return
 
         missing_items = {
@@ -113,16 +111,16 @@ def enforce_required_fields(self, attrs, instance):
         if missing_items:
             raise ValidationError(missing_items, code='required')
 
-    def filter_queryset(self, attrs, queryset, instance):
+    def filter_queryset(self, attrs, queryset, serializer):
         """
         Filter the queryset to all instances matching the given attributes.
         """
         # If this is an update, then any unprovided field should
         # have it's value set based on the existing instance attribute.
-        if instance is not None:
+        if serializer.instance is not None:
             for field_name in self.fields:
                 if field_name not in attrs:
-                    attrs[field_name] = getattr(instance, field_name)
+                    attrs[field_name] = getattr(serializer.instance, field_name)
 
         # Determine the filter keyword arguments and filter the queryset.
         filter_kwargs = {
@@ -141,13 +139,10 @@ def exclude_current_instance(self, attrs, queryset, instance):
         return queryset
 
     def __call__(self, attrs, serializer):
-        # Determine the existing instance, if this is an update operation.
-        instance = getattr(serializer, 'instance', None)
-
-        self.enforce_required_fields(attrs, instance)
+        self.enforce_required_fields(attrs, serializer)
         queryset = self.queryset
-        queryset = self.filter_queryset(attrs, queryset, instance)
-        queryset = self.exclude_current_instance(attrs, queryset, instance)
+        queryset = self.filter_queryset(attrs, queryset, serializer)
+        queryset = self.exclude_current_instance(attrs, queryset, serializer.instance)
 
         # Ignore validation if any field is None
         checked_values = [
@@ -207,13 +202,11 @@ def __call__(self, attrs, serializer):
         # same as the serializer field names if `source=<>` is set.
         field_name = serializer.fields[self.field].source_attrs[-1]
         date_field_name = serializer.fields[self.date_field].source_attrs[-1]
-        # Determine the existing instance, if this is an update operation.
-        instance = getattr(serializer, 'instance', None)
 
         self.enforce_required_fields(attrs)
         queryset = self.queryset
         queryset = self.filter_queryset(attrs, queryset, field_name, date_field_name)
-        queryset = self.exclude_current_instance(attrs, queryset, instance)
+        queryset = self.exclude_current_instance(attrs, queryset, serializer.instance)
         if qs_exists(queryset):
             message = self.message.format(date_field=self.date_field)
             raise ValidationError({
diff --git a/tests/test_fields.py b/tests/test_fields.py
index 1d302b730e..0be1b1a7a0 100644
--- a/tests/test_fields.py
+++ b/tests/test_fields.py
@@ -565,11 +565,10 @@ def test_create_only_default_callable_sets_context(self):
         on the callable if possible
         """
         class TestCallableDefault:
-            def set_context(self, serializer_field):
-                self.field = serializer_field
+            requires_context = True
 
-            def __call__(self):
-                return "success" if hasattr(self, 'field') else "failure"
+            def __call__(self, field=None):
+                return "success" if field is not None else "failure"
 
         class TestSerializer(serializers.Serializer):
             context_set = serializers.CharField(default=serializers.CreateOnlyDefault(TestCallableDefault()))
diff --git a/tests/test_validators.py b/tests/test_validators.py
index bb29a4305b..5c4a62b314 100644
--- a/tests/test_validators.py
+++ b/tests/test_validators.py
@@ -357,11 +357,16 @@ class MockQueryset:
             def filter(self, **kwargs):
                 self.called_with = kwargs
 
+        class MockSerializer:
+            def __init__(self, instance):
+                self.instance = instance
+
         data = {'race_name': 'bar'}
         queryset = MockQueryset()
+        serializer = MockSerializer(instance=self.instance)
         validator = UniqueTogetherValidator(queryset, fields=('race_name',
                                                               'position'))
-        validator.filter_queryset(attrs=data, queryset=queryset, instance=self.instance)
+        validator.filter_queryset(attrs=data, queryset=queryset, serializer=serializer)
         assert queryset.called_with == {'race_name': 'bar', 'position': 1}