diff --git a/services/acl/Acl.IntegrationTests/OpenZaakGatewayIntegrationTests.cs b/services/acl/Acl.IntegrationTests/OpenZaakGatewayIntegrationTests.cs
index d59d0d9..70c84bf 100644
--- a/services/acl/Acl.IntegrationTests/OpenZaakGatewayIntegrationTests.cs
+++ b/services/acl/Acl.IntegrationTests/OpenZaakGatewayIntegrationTests.cs
@@ -161,4 +161,32 @@ public sealed class OpenZaakGatewayIntegrationTests(OpenZaakFixture stack)
         Assert.Contains(relations.EnumerateArray(),
             r => r.GetProperty("zaak").GetString() == zaakUrl.ToString());
     }
+
+    [Fact]
+    public async Task Resolves_the_published_zaaktype_and_diploma_informatieobjecttype_by_business_key()
+    {
+        var expectedZaaktype = await stack.FindPublishedBigZaaktypeAsync();
+        Assert.True(expectedZaaktype is not null,
+            "No published BIG-REGISTRATIE zaaktype found — seed the stack with OZ_PUBLISH=1.");
+        var expectedInformatieobjecttype = await stack.FindPublishedDiplomaInformatieobjecttypeAsync();
+        Assert.True(expectedInformatieobjecttype is not null,
+            "No published Diploma informatieobjecttype found — seed the stack with OZ_PUBLISH=1.");
+
+        var gateway = new OpenZaakGateway(stack.Http, stack.Options);
+
+        // The ACL discovers both URLs from the live Catalogi API by their stable business keys (S-27),
+        // matching what the fixture found independently — no pinned URL needed.
+        Assert.Equal(expectedZaaktype, await gateway.ResolveZaaktypeUrlAsync("BIG-REGISTRATIE"));
+        Assert.Equal(expectedInformatieobjecttype, await gateway.ResolveInformatieobjecttypeUrlAsync("Diploma"));
+    }
+
+    [Fact]
+    public async Task Resolving_an_unknown_zaaktype_identificatie_throws_a_clear_error()
+    {
+        var gateway = new OpenZaakGateway(stack.Http, stack.Options);
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+            () => gateway.ResolveZaaktypeUrlAsync("NO-SUCH-ZAAKTYPE"));
+        Assert.Contains("NO-SUCH-ZAAKTYPE", ex.Message);
+    }
 }