diff --git a/goextVersion.go b/goextVersion.go
index ca48575..f80ddd6 100644
--- a/goextVersion.go
+++ b/goextVersion.go
@@ -1,5 +1,5 @@
 package goext
 
-const GoextVersion = "0.0.154"
+const GoextVersion = "0.0.155"
 
-const GoextVersionTimestamp = "2023-06-08T16:24:53+0200"
+const GoextVersionTimestamp = "2023-06-08T16:26:06+0200"
diff --git a/wmo/collection.go b/wmo/collection.go
index 4fb117f..cfcfaf9 100644
--- a/wmo/collection.go
+++ b/wmo/collection.go
@@ -2,13 +2,17 @@ package wmo
 
 import (
 	"context"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
 	"go.mongodb.org/mongo-driver/mongo"
 	ct "gogs.mikescher.com/BlackForestBytes/goext/cursortoken"
 	"gogs.mikescher.com/BlackForestBytes/goext/langext"
 	"reflect"
 )
 
-type EntityID = any
+type EntityID interface {
+	MarshalBSONValue() (bsontype.Type, []byte, error)
+	String() string
+}
 
 type fullTypeRef[TData any] struct {
 	IsPointer      bool