diff --git a/src/openforms/validations/registry.py b/src/openforms/validations/registry.py
index 08a7819edb..8bfe462887 100644
--- a/src/openforms/validations/registry.py
+++ b/src/openforms/validations/registry.py
@@ -59,8 +59,9 @@ def _flat(it):
 
 def filter_empty_values(value: Any) -> Any:
     if not isinstance(value, dict):
-        # Let the serializer raise a the validation error
+        # Let the serializer raise the validation error
         return value
+
     return {k: v for k, v in value.items() if v}
 
 
@@ -141,7 +142,6 @@ def validate(
         SerializerClass = validator.callable.value_serializer
         serializer = SerializerClass(data={"value": filter_empty_values(value)})
         serializer.is_valid(raise_exception=True)
-
         try:
             validator(serializer.data["value"], submission)
         except (DJ_ValidationError, DRF_ValidationError) as e:
diff --git a/src/openforms/validations/tests/test_api.py b/src/openforms/validations/tests/test_api.py
index a4ce880a1a..fc7c735670 100644
--- a/src/openforms/validations/tests/test_api.py
+++ b/src/openforms/validations/tests/test_api.py
@@ -11,6 +11,7 @@
 from openforms.submissions.tests.factories import SubmissionFactory
 from openforms.validations.registry import Registry, StringValueSerializer
 from openforms.validations.tests.test_registry import (
+    DictValidator,
     DjangoValidator,
     DRFValidator,
     function_validator,
@@ -38,6 +39,12 @@ def setUp(self):
             "demo", verbose_name="Demo function", for_components=(), is_demo_plugin=True
         )(function_validator)
 
+        register(
+            "dict_validator",
+            verbose_name="Dict validator",
+            for_components=("addressNL",),
+        )(DictValidator)
+
         patcher = patch("openforms.validations.api.views.register", new=register)
         patcher.start()
         self.addCleanup(patcher.stop)
@@ -76,6 +83,11 @@ def test_validations_list(self):
                         "label": "Django function Validator",
                         "for_components": [],
                     },
+                    {
+                        "id": "dict_validator",
+                        "label": "Dict validator",
+                        "for_components": ["addressNL"],
+                    },
                 ],
             )
 
@@ -137,6 +149,11 @@ def test_validations_list(self):
                         "label": "Django function Validator",
                         "for_components": [],
                     },
+                    {
+                        "id": "dict_validator",
+                        "label": "Dict validator",
+                        "for_components": ["addressNL"],
+                    },
                 ],
             )
 
@@ -154,6 +171,16 @@ def test_default_string_serializer(self):
         self.assertFalse(StringValueSerializer(data={"value": None}).is_valid())
         self.assertFalse(StringValueSerializer(data={"bazz": "buzz"}).is_valid())
 
+    def test_validation_forbidden(self):
+        submission = SubmissionFactory.create()
+        submission_uuid = str(submission.uuid)
+        url = reverse("api:validate-value", kwargs={"validator": "django"})
+
+        response = self.client.post(
+            url, {"value": "VALID", "submission_uuid": submission_uuid}, format="json"
+        )
+        self.assertEqual(response.status_code, 403)
+
     def test_validation(self):
         submission = SubmissionFactory.create()
         submission_uuid = str(submission.uuid)
@@ -183,3 +210,27 @@ def test_validation(self):
         }
         self.assertEqual(response.status_code, 200)
         self.assertEqual(response.data, expected)
+
+    def test_validation_dict(self):
+        # This test exists to add coverage to the `filter_empty_values` function
+        submission = SubmissionFactory.create()
+        submission_uuid = str(submission.uuid)
+        url = reverse("api:validate-value", kwargs={"validator": "dict_validator"})
+        session = self.client.session
+        session[SUBMISSIONS_SESSION_KEY] = [submission_uuid]
+        session.save()
+
+        response = self.client.post(
+            url,
+            {
+                "value": {"field": "dummy", "extra": ""},
+                "submission_uuid": submission_uuid,
+            },
+            format="json",
+        )
+        expected = {
+            "is_valid": True,
+            "messages": [],
+        }
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(response.data, expected)
diff --git a/src/openforms/validations/tests/test_registry.py b/src/openforms/validations/tests/test_registry.py
index a0ae27fa5b..75cad324a6 100644
--- a/src/openforms/validations/tests/test_registry.py
+++ b/src/openforms/validations/tests/test_registry.py
@@ -2,11 +2,20 @@
 from django.test import TestCase
 from django.utils.translation import gettext as _
 
+from rest_framework import serializers
 from rest_framework.exceptions import ValidationError as DRFValidationError
 
 from openforms.validations.registry import Registry, StringValueSerializer
 
 
+class DummyDataSerializer(serializers.Serializer):
+    field = serializers.CharField()
+
+
+class DictValueSerializer(serializers.Serializer):
+    value = DummyDataSerializer()
+
+
 class DjangoValidator:
     is_enabled = True
     components = ("textfield",)
@@ -37,6 +46,14 @@ def __call__(self, value, submission):
             raise DRFValidationError("not VALID value")
 
 
+class DictValidator:
+    is_enabled = True
+    value_serializer = DictValueSerializer
+
+    def __call__(self, value, submission):
+        return True
+
+
 def function_validator(value, submission):
     if value != "VALID":
         raise DjangoValidationError("not VALID value")