diff --git a/src/openforms/contrib/objects_api/migrations/0006_alter_objectsapigroupconfig_catalogue_domain.py b/src/openforms/contrib/objects_api/migrations/0006_alter_objectsapigroupconfig_catalogue_domain.py
new file mode 100644
index 0000000000..61f74611ac
--- /dev/null
+++ b/src/openforms/contrib/objects_api/migrations/0006_alter_objectsapigroupconfig_catalogue_domain.py
@@ -0,0 +1,23 @@
+# Generated by Django 4.2.18 on 2025-02-03 20:21
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("objects_api", "0005_alter_objectsapigroupconfig_table"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="objectsapigroupconfig",
+            name="catalogue_domain",
+            field=models.CharField(
+                blank=True,
+                help_text="The 'domein' attribute for the Catalogus resource in the Catalogi API.",
+                max_length=5,
+                verbose_name="catalogus domain",
+            ),
+        ),
+    ]
diff --git a/src/openforms/contrib/objects_api/models.py b/src/openforms/contrib/objects_api/models.py
index 9483e39036..fadf15b075 100644
--- a/src/openforms/contrib/objects_api/models.py
+++ b/src/openforms/contrib/objects_api/models.py
@@ -3,7 +3,7 @@
 
 from zgw_consumers.constants import APITypes
 
-from openforms.utils.validators import RSINValidator, validate_rsin, validate_uppercase
+from openforms.utils.validators import RSINValidator, validate_rsin
 
 # no catalogus specified, requires both RSIN and domain to be unspecified
 _CATALOGUE_NOT_SET = models.Q(catalogue_domain="", catalogue_rsin="")
@@ -75,7 +75,6 @@ class ObjectsAPIGroupConfig(models.Model):
         help_text=_(
             "The 'domein' attribute for the Catalogus resource in the Catalogi API."
         ),
-        validators=[validate_uppercase],
     )
     catalogue_rsin = models.CharField(
         _("catalogus RSIN"),
diff --git a/src/openforms/contrib/zgw/serializers.py b/src/openforms/contrib/zgw/serializers.py
index cdf289285f..df20f9d0b0 100644
--- a/src/openforms/contrib/zgw/serializers.py
+++ b/src/openforms/contrib/zgw/serializers.py
@@ -3,7 +3,7 @@
 from rest_framework import serializers
 
 from openforms.api.validators import AllOrNoneTruthyFieldsValidator
-from openforms.utils.validators import RSINValidator, validate_uppercase
+from openforms.utils.validators import RSINValidator
 
 
 class CatalogueSerializer(serializers.Serializer):
@@ -29,7 +29,6 @@ class CatalogueSerializer(serializers.Serializer):
             "The 'domein' attribute for the Catalogus resource in the Catalogi API."
         ),
         default="",
-        validators=[validate_uppercase],
         allow_blank=True,
     )
     rsin = serializers.CharField(
diff --git a/src/openforms/registrations/contrib/zgw_apis/migrations/0019_alter_zgwapigroupconfig_catalogue_domain.py b/src/openforms/registrations/contrib/zgw_apis/migrations/0019_alter_zgwapigroupconfig_catalogue_domain.py
new file mode 100644
index 0000000000..0a6b5290ee
--- /dev/null
+++ b/src/openforms/registrations/contrib/zgw_apis/migrations/0019_alter_zgwapigroupconfig_catalogue_domain.py
@@ -0,0 +1,23 @@
+# Generated by Django 4.2.18 on 2025-02-03 20:21
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("zgw_apis", "0018_alter_zgwapigroupconfig_drc_service_and_more"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="zgwapigroupconfig",
+            name="catalogue_domain",
+            field=models.CharField(
+                blank=True,
+                help_text="The 'domein' attribute for the Catalogus resource in the Catalogi API.",
+                max_length=5,
+                verbose_name="catalogus domain",
+            ),
+        ),
+    ]
diff --git a/src/openforms/registrations/contrib/zgw_apis/migrations/0020_merge_20250204_1209.py b/src/openforms/registrations/contrib/zgw_apis/migrations/0020_merge_20250204_1209.py
new file mode 100644
index 0000000000..600da79368
--- /dev/null
+++ b/src/openforms/registrations/contrib/zgw_apis/migrations/0020_merge_20250204_1209.py
@@ -0,0 +1,13 @@
+# Generated by Django 4.2.18 on 2025-02-04 11:09
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("zgw_apis", "0019_alter_zgwapigroupconfig_auteur"),
+        ("zgw_apis", "0019_alter_zgwapigroupconfig_catalogue_domain"),
+    ]
+
+    operations = []
diff --git a/src/openforms/registrations/contrib/zgw_apis/models.py b/src/openforms/registrations/contrib/zgw_apis/models.py
index 6a866f7bf3..d0a5a7047c 100644
--- a/src/openforms/registrations/contrib/zgw_apis/models.py
+++ b/src/openforms/registrations/contrib/zgw_apis/models.py
@@ -7,7 +7,7 @@
 from zgw_consumers.constants import APITypes
 
 from openforms.template.validators import DjangoTemplateValidator
-from openforms.utils.validators import RSINValidator, validate_rsin, validate_uppercase
+from openforms.utils.validators import RSINValidator, validate_rsin
 
 
 def get_content_text() -> str:
@@ -98,7 +98,6 @@ class ZGWApiGroupConfig(models.Model):
         help_text=_(
             "The 'domein' attribute for the Catalogus resource in the Catalogi API."
         ),
-        validators=[validate_uppercase],
     )
     catalogue_rsin = models.CharField(
         _("catalogus RSIN"),
diff --git a/src/openforms/utils/validators.py b/src/openforms/utils/validators.py
index 5db3edb923..173b271bbd 100644
--- a/src/openforms/utils/validators.py
+++ b/src/openforms/utils/validators.py
@@ -13,13 +13,6 @@
 )
 
 
-validate_uppercase = RegexValidator(
-    r"^[A-Z]*$",
-    message=_("Value must be all uppercase letters."),
-    code="invalid",
-)
-
-
 class Proef11ValidatorBase:
     value_size = NotImplemented
     error_messages = {