diff --git a/authentik/crypto/api.py b/authentik/crypto/api.py
index 5bd2665347..ed31e82137 100644
--- a/authentik/crypto/api.py
+++ b/authentik/crypto/api.py
@@ -24,6 +24,7 @@ from rest_framework.fields import (
 from rest_framework.filters import OrderingFilter, SearchFilter
 from rest_framework.request import Request
 from rest_framework.response import Response
+from rest_framework.validators import UniqueValidator
 from rest_framework.viewsets import ModelViewSet
 from structlog.stdlib import get_logger
 
@@ -181,7 +182,10 @@ class CertificateDataSerializer(PassiveSerializer):
 class CertificateGenerationSerializer(PassiveSerializer):
     """Certificate generation parameters"""
 
-    common_name = CharField()
+    common_name = CharField(
+        validators=[UniqueValidator(queryset=CertificateKeyPair.objects.all())],
+        source="name",
+    )
     subject_alt_name = CharField(required=False, allow_blank=True, label=_("Subject-alt name"))
     validity_days = IntegerField(initial=365)
     alg = ChoiceField(default=PrivateKeyAlg.RSA, choices=PrivateKeyAlg.choices)
@@ -242,11 +246,10 @@ class CertificateKeyPairViewSet(UsedByMixin, ModelViewSet):
     def generate(self, request: Request) -> Response:
         """Generate a new, self-signed certificate-key pair"""
         data = CertificateGenerationSerializer(data=request.data)
-        if not data.is_valid():
-            return Response(data.errors, status=400)
+        data.is_valid(raise_exception=True)
         raw_san = data.validated_data.get("subject_alt_name", "")
         sans = raw_san.split(",") if raw_san != "" else []
-        builder = CertificateBuilder(data.validated_data["common_name"])
+        builder = CertificateBuilder(data.validated_data["name"])
         builder.alg = data.validated_data["alg"]
         builder.build(
             subject_alt_names=sans,
diff --git a/authentik/crypto/tests.py b/authentik/crypto/tests.py
index e2dc755e7c..bb0c1b4e31 100644
--- a/authentik/crypto/tests.py
+++ b/authentik/crypto/tests.py
@@ -89,6 +89,17 @@ class TestCrypto(APITestCase):
         self.assertIsInstance(ext[1], DNSName)
         self.assertEqual(ext[1].value, "baz")
 
+    def test_builder_api_duplicate(self):
+        """Test Builder (via API)"""
+        cert = create_test_cert()
+        self.client.force_login(create_test_admin_user())
+        res = self.client.post(
+            reverse("authentik_api:certificatekeypair-generate"),
+            data={"common_name": cert.name, "subject_alt_name": "bar,baz", "validity_days": 3},
+        )
+        self.assertEqual(res.status_code, 400)
+        self.assertJSONEqual(res.content, {"common_name": ["This field must be unique."]})
+
     def test_builder_api_empty_san(self):
         """Test Builder (via API)"""
         self.client.force_login(create_test_admin_user())