diff --git a/src/Squidex.Domain.Apps.Entities/Contents/Text/GrainTextIndexer.cs b/src/Squidex.Domain.Apps.Entities/Contents/Text/GrainTextIndexer.cs
index fe005a4a37..f4b3ab2232 100644
--- a/src/Squidex.Domain.Apps.Entities/Contents/Text/GrainTextIndexer.cs
+++ b/src/Squidex.Domain.Apps.Entities/Contents/Text/GrainTextIndexer.cs
@@ -56,6 +56,11 @@ public async Task On(Envelope<IEvent> @event)
             if (@event.Payload is ContentEvent contentEvent)
             {
                 var index = grainFactory.GetGrain<ITextIndexerGrain>(contentEvent.SchemaId.Id);
+                
+                if (index == null)
+                {
+                    throw new InvalidOperationException("Cannot create reference to grain.");
+                }
 
                 var id = contentEvent.ContentId;