diff --git a/services/acl/Acl.Tests/OpenZaakGatewayTests.cs b/services/acl/Acl.Tests/OpenZaakGatewayTests.cs
index 081701c..142a318 100644
--- a/services/acl/Acl.Tests/OpenZaakGatewayTests.cs
+++ b/services/acl/Acl.Tests/OpenZaakGatewayTests.cs
@@ -824,4 +824,51 @@ public class OpenZaakGatewayTests
         await Assert.ThrowsAnyAsync<ArgumentException>(() => Gateway(handler).ResolveZaaktypeUrlAsync(" "));
         await Assert.ThrowsAnyAsync<ArgumentException>(() => Gateway(handler).ResolveInformatieobjecttypeUrlAsync(" "));
     }
+
+    [Fact]
+    public async Task Listing_zaaktypen_queries_published_zaaktypen_and_maps_them(/* S-15a */)
+    {
+        HttpRequestMessage? seen = null;
+        var handler = new StubHandler(req =>
+        {
+            seen = req;
+            const string json = """
+                {"results":[
+                  {"url":"http://openzaak/catalogi/api/v1/zaaktypen/big","identificatie":"BIG-REGISTRATIE","omschrijving":"BIG-registratie"},
+                  {"url":"http://openzaak/catalogi/api/v1/zaaktypen/her","identificatie":"BIG-HERREGISTRATIE","omschrijving":"BIG-herregistratie"}
+                ]}
+                """;
+            return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+            {
+                Content = new StringContent(json, Encoding.UTF8, "application/json"),
+            });
+        });
+
+        var zaaktypen = await Gateway(handler).ListZaaktypenAsync();
+
+        // Only the published zaaktypen collection is queried (status=definitief excludes concepts).
+        Assert.Contains("/catalogi/api/v1/zaaktypen", seen!.RequestUri!.ToString());
+        Assert.Contains("status=definitief", seen.RequestUri!.ToString());
+        // Authenticated like the other catalogi reads.
+        Assert.Equal("Bearer", seen.Headers.Authorization!.Scheme);
+        // Each result maps to a public-safe summary (identificatie + omschrijving + url).
+        Assert.Equal(2, zaaktypen.Count);
+        Assert.Equal("BIG-REGISTRATIE", zaaktypen[0].Identificatie);
+        Assert.Equal("BIG-registratie", zaaktypen[0].Omschrijving);
+        Assert.Equal(new Uri("http://openzaak/catalogi/api/v1/zaaktypen/big"), zaaktypen[0].Url);
+        Assert.Equal("BIG-HERREGISTRATIE", zaaktypen[1].Identificatie);
+    }
+
+    [Fact]
+    public async Task Listing_zaaktypen_returns_empty_when_the_catalogus_has_none()
+    {
+        var handler = new StubHandler(_ => Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+        {
+            Content = new StringContent("""{"results":[]}""", Encoding.UTF8, "application/json"),
+        }));
+
+        var zaaktypen = await Gateway(handler).ListZaaktypenAsync();
+
+        Assert.Empty(zaaktypen);
+    }
 }