diff --git a/backend/src/Squidex.Domain.Apps.Core.Operations/HandleRules/RuleActionHandler.cs b/backend/src/Squidex.Domain.Apps.Core.Operations/HandleRules/RuleActionHandler.cs
index 7f5ac7c90..136045189 100644
--- a/backend/src/Squidex.Domain.Apps.Core.Operations/HandleRules/RuleActionHandler.cs
+++ b/backend/src/Squidex.Domain.Apps.Core.Operations/HandleRules/RuleActionHandler.cs
@@ -31,7 +31,7 @@ namespace Squidex.Domain.Apps.Core.HandleRules
             this.formatter = formatter;
         }
 
-        protected virtual string ToJson<T>(T @event)
+        protected virtual string ToJson<T>(T @event) where T : notnull
         {
             return formatter.ToPayload(@event);
         }
diff --git a/backend/src/Squidex.Domain.Apps.Core.Operations/HandleRules/RuleEventFormatter.cs b/backend/src/Squidex.Domain.Apps.Core.Operations/HandleRules/RuleEventFormatter.cs
index 63db6c6b5..fc969406a 100644
--- a/backend/src/Squidex.Domain.Apps.Core.Operations/HandleRules/RuleEventFormatter.cs
+++ b/backend/src/Squidex.Domain.Apps.Core.Operations/HandleRules/RuleEventFormatter.cs
@@ -78,10 +78,10 @@ namespace Squidex.Domain.Apps.Core.HandleRules
             this.scriptEngine = scriptEngine;
         }
 
-        public virtual string ToPayload<T>(T @event)
+        public virtual string ToPayload<T>(T @event) where T : notnull
         {
             // Just serialize the payload.
-            return serializer.Serialize(@event, true);
+            return serializer.Serialize((object)@event, true);
         }
 
         public virtual string ToEnvelope(EnrichedEvent @event)
diff --git a/backend/src/Squidex.Infrastructure/Squidex.Infrastructure.csproj b/backend/src/Squidex.Infrastructure/Squidex.Infrastructure.csproj
index f4159ca80..07cdd4819 100644
--- a/backend/src/Squidex.Infrastructure/Squidex.Infrastructure.csproj
+++ b/backend/src/Squidex.Infrastructure/Squidex.Infrastructure.csproj
@@ -27,7 +27,7 @@
     <PackageReference Include="Squidex.Caching" Version="1.9.0" />
     <PackageReference Include="Squidex.Hosting.Abstractions" Version="2.13.0" />
     <PackageReference Include="Squidex.Log" Version="1.6.0" />
-    <PackageReference Include="Squidex.Messaging" Version="2.2.0" />
+    <PackageReference Include="Squidex.Messaging" Version="2.1.0" />
     <PackageReference Include="Squidex.Text" Version="1.7.0" />
     <PackageReference Include="StyleCop.Analyzers" Version="1.1.118" PrivateAssets="all" />
     <PackageReference Include="System.Collections.Immutable" Version="6.0.0" />