diff --git a/src/TextServices.Builder.Api/Services/Notifications/SnsJobNotifier.cs b/src/TextServices.Builder.Api/Services/Notifications/SnsJobNotifier.cs
index 3391275..24e4fc8 100644
--- a/src/TextServices.Builder.Api/Services/Notifications/SnsJobNotifier.cs
+++ b/src/TextServices.Builder.Api/Services/Notifications/SnsJobNotifier.cs
@@ -1,4 +1,5 @@
 using System.Text.Json;
+using System.Text.Json.Serialization;
 using Amazon.SimpleNotificationService;
 using Amazon.SimpleNotificationService.Model;
 using Microsoft.Extensions.Options;
@@ -12,6 +13,13 @@ internal sealed class SnsJobNotifier(
     IOptions<TextServicesOptions> options,
     ILogger<SnsJobNotifier> logger) : IJobNotifier
 {
+    private static readonly JsonSerializerOptions SerializerOptions = new()
+    {
+        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+        Converters = { new JsonStringEnumConverter() },
+        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
+    };
+
     public async Task Notify(JobCompletionNotification notification, CancellationToken ct = default)
     {
         var topicArn = options.Value.Notifications.TopicArn;
@@ -25,7 +33,7 @@ public async Task Notify(JobCompletionNotification notification, CancellationTok
             await sns.PublishAsync(new PublishRequest
             {
                 TopicArn = topicArn,
-                Message = JsonSerializer.Serialize(notification),
+                Message = JsonSerializer.Serialize(notification, SerializerOptions),
                 MessageAttributes = new Dictionary<string, MessageAttributeValue>
                 {
                     ["MessageType"] = new()
diff --git a/src/TextServices.Builder.Api/TextServices.Builder.Api.csproj b/src/TextServices.Builder.Api/TextServices.Builder.Api.csproj
index 2d4814a..7a1c499 100644
--- a/src/TextServices.Builder.Api/TextServices.Builder.Api.csproj
+++ b/src/TextServices.Builder.Api/TextServices.Builder.Api.csproj
@@ -16,7 +16,7 @@
     <PackageReference Include="Hangfire.AspNetCore" Version="1.8.23" />
     <PackageReference Include="Hangfire.PostgreSql" Version="1.21.1" />
     <PackageReference Include="iiif-net" Version="0.3.13" />
-    <PackageReference Include="MediatR" Version="13.1.0" />
+    <PackageReference Include="MediatR" Version="12.5.0" />
     <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="10.0.1" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="10.0.5">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
diff --git a/src/TextServices.Search.Api/TextServices.Search.Api.csproj b/src/TextServices.Search.Api/TextServices.Search.Api.csproj
index 9a111c4..2fa1628 100644
--- a/src/TextServices.Search.Api/TextServices.Search.Api.csproj
+++ b/src/TextServices.Search.Api/TextServices.Search.Api.csproj
@@ -10,7 +10,7 @@
     <PackageReference Include="AsyncKeyedLock" Version="8.0.2" />
     <PackageReference Include="AWSSDK.Extensions.NETCore.Setup" Version="4.0.0.0" />
     <PackageReference Include="AWSSDK.SecurityToken" Version="4.0.6.8" />
-    <PackageReference Include="MediatR" Version="13.1.0" />
+    <PackageReference Include="MediatR" Version="12.5.0" />
     <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="10.0.1" />
     <PackageReference Include="Serilog.AspNetCore" Version="10.0.0" />
     <PackageReference Include="Serilog.Enrichers.ClientInfo" Version="2.9.0" />
diff --git a/src/TextServices.Tests/BuilderApi/SnsJobNotifierTests.cs b/src/TextServices.Tests/BuilderApi/SnsJobNotifierTests.cs
index 4efcf60..18ce0e6 100644
--- a/src/TextServices.Tests/BuilderApi/SnsJobNotifierTests.cs
+++ b/src/TextServices.Tests/BuilderApi/SnsJobNotifierTests.cs
@@ -78,6 +78,26 @@ public async Task Notify_SetsMessageTypeAttribute(JobStatus status, string expec
             .MustHaveHappenedOnceExactly();
     }
 
+    [Fact]
+    public async Task Notify_SerialisesMessageWithCamelCaseStringEnumAndOmitsNullErrors()
+    {
+        var sns = A.Fake<IAmazonSimpleNotificationService>();
+        PublishRequest? captured = null;
+        A.CallTo(() => sns.PublishAsync(A<PublishRequest>._, A<CancellationToken>._))
+            .Invokes((PublishRequest r, CancellationToken _) => captured = r)
+            .Returns(new PublishResponse());
+
+        var sut = MakeNotifier(sns, "arn:aws:sns:eu-west-1:123:test-topic");
+
+        await sut.Notify(MakeNotification("books/b123", JobStatus.Waiting));
+
+        captured.ShouldNotBeNull();
+        var message = captured.Message;
+        message.ShouldContain("\"jobId\":\"books/b123\"");
+        message.ShouldContain("\"status\":\"Waiting\"");
+        message.ShouldNotContain("errors");
+    }
+
     // -------------------------------------------------------------------------
     // Error handling
     // -------------------------------------------------------------------------