diff --git a/src/Marten/Events/Aggregation/AggregationRuntime.cs b/src/Marten/Events/Aggregation/AggregationRuntime.cs
index 2c667e3eda..e14da4cb19 100644
--- a/src/Marten/Events/Aggregation/AggregationRuntime.cs
+++ b/src/Marten/Events/Aggregation/AggregationRuntime.cs
@@ -325,7 +325,7 @@ public IAggregateCache<TId, TDoc> CacheFor(Tenant tenant)
         }
     }
 
-    public TId IdentityFromEvent(IEvent e)
+    public TId IdentityFromEvent(StreamIdentity streamIdentity, IEvent e)
     {
         return _identitySource(e);
     }
diff --git a/src/Marten/Events/Aggregation/IAggregationRuntime.cs b/src/Marten/Events/Aggregation/IAggregationRuntime.cs
index 99518e70f3..0948310c2f 100644
--- a/src/Marten/Events/Aggregation/IAggregationRuntime.cs
+++ b/src/Marten/Events/Aggregation/IAggregationRuntime.cs
@@ -40,5 +40,5 @@ ValueTask ApplyChangesAsync(DocumentSessionBase session,
 
     IAggregateCache<TId, TDoc> CacheFor(Tenant tenant);
 
-    TId IdentityFromEvent(IEvent e);
+    TId IdentityFromEvent(StreamIdentity streamIdentity, IEvent e);
 }
diff --git a/src/Marten/Events/Aggregation/Rebuilds/AggregatePageHandler.cs b/src/Marten/Events/Aggregation/Rebuilds/AggregatePageHandler.cs
index 19221a2545..ad9c367fff 100644
--- a/src/Marten/Events/Aggregation/Rebuilds/AggregatePageHandler.cs
+++ b/src/Marten/Events/Aggregation/Rebuilds/AggregatePageHandler.cs
@@ -192,7 +192,7 @@ private async Task collateAndPostSlices(IAsyncEnumerable<IEvent> events, ITarget
         EventSlice<TDoc, TId> slice = null;
         await foreach (var e in events)
         {
-            var aggregateId = _runtime.IdentityFromEvent(e);
+            var aggregateId = _runtime.IdentityFromEvent(_session.Options.Events.StreamIdentity, e);
             slice ??= new EventSlice<TDoc, TId>(aggregateId, _session);
 
             if (!slice.Id.Equals(aggregateId))