diff --git a/src/Utils/Data/Immutable/ImmutableTree.cs b/src/Utils/Data/Immutable/ImmutableTree.cs
index 7e84f759..cd6a4424 100644
--- a/src/Utils/Data/Immutable/ImmutableTree.cs
+++ b/src/Utils/Data/Immutable/ImmutableTree.cs
@@ -408,11 +408,12 @@ private ImmutableTree<TKey, TValue> CheckCollision(int hash, TKey key, TValue va
             return new ImmutableTree<TKey, TValue>(hash, this.storedKey!, this.storedValue!, this.leftNode!, this.rightNode!,
                 ImmutableBucket<TKey, TValue>.Empty.Add(key, value));
 
-        var @new = updateDelegate == null || forceUpdate
+        var collision = byRef ? this.collisions.GetOrDefaultByRef(key) : this.collisions.GetOrDefaultByValue(key);
+        var @new = collision == null || updateDelegate == null || forceUpdate
             ? value
-            : updateDelegate(this.storedValue!, value);
+            : updateDelegate(collision, value);
 
-        if (ReferenceEquals(@new, this.storedValue))
+        if (ReferenceEquals(@new, collision))
             return this;
 
         return new ImmutableTree<TKey, TValue>(hash, this.storedKey!, this.storedValue!, this.leftNode!, this.rightNode!,
@@ -738,4 +739,4 @@ internal class ImmutableRefTreeDebugView<TValue> where TValue : class
 
     [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
     public TValue[] Items => tree.Walk().ToArray();
-}
\ No newline at end of file
+}
diff --git a/test/DataTests/TreeTests.cs b/test/DataTests/TreeTests.cs
index 5c58648a..5a3e9f30 100644
--- a/test/DataTests/TreeTests.cs
+++ b/test/DataTests/TreeTests.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using Stashbox.Tests.Utils;
 using Stashbox.Utils.Data;
 using Stashbox.Utils.Data.Immutable;
@@ -17,38 +18,38 @@ public void Test_Collision_Check()
         var a = new A();
         var b = new B();
         var c = new C();
-        var imTree = ImmutableTree<object, object>.Empty;
-        var tree = new HashTree<object, object>();
+        var imTree = ImmutableTree<object, List<object>>.Empty;
+        var tree = new HashTree<object, List<object>>();
 
-        imTree = imTree.AddOrUpdate(key1, a, false);
-        imTree = imTree.AddOrUpdate(key2, b, false);
-        tree.Add(key1, a);
-        tree.Add(key2, b);
-        
-        Assert.Equal(a, imTree.GetOrDefaultByValue(key1));
-        Assert.Equal(b, imTree.GetOrDefaultByValue(key2));
-        Assert.Equal(a, tree.GetOrDefault(key1));
-        Assert.Equal(b, tree.GetOrDefault(key2));
+        imTree = imTree.AddOrUpdate(key1, [a], false);
+        imTree = imTree.AddOrUpdate(key2, [b], false);
+        tree.Add(key1, [a]);
+        tree.Add(key2, [b]);
+        
+        Assert.Equal([a], imTree.GetOrDefaultByValue(key1));
+        Assert.Equal([b], imTree.GetOrDefaultByValue(key2));
+        Assert.Equal([a], tree.GetOrDefault(key1));
+        Assert.Equal([b], tree.GetOrDefault(key2));
 
-        imTree = imTree.AddOrUpdate(key2, c, false, (_, n) => n);
+        imTree = imTree.AddOrUpdate(key2, [c], false, (list, n) => [..list, ..n]);
         
-        Assert.Equal(a, imTree.GetOrDefaultByValue(key1));
-        Assert.Equal(c, imTree.GetOrDefaultByValue(key2));
+        Assert.Equal([a], imTree.GetOrDefaultByValue(key1));
+        Assert.Equal([b, c], imTree.GetOrDefaultByValue(key2));
 
-        imTree = imTree.AddOrUpdate(key2, b, false, true);
+        imTree = imTree.AddOrUpdate(key2, [b], false, true);
         
-        Assert.Equal(a, imTree.GetOrDefaultByValue(key1));
-        Assert.Equal(b, imTree.GetOrDefaultByValue(key2));
+        Assert.Equal([a], imTree.GetOrDefaultByValue(key1));
+        Assert.Equal([b], imTree.GetOrDefaultByValue(key2));
         
-        imTree = imTree.UpdateIfExists(key2, false, _ => c);
+        imTree = imTree.UpdateIfExists(key2, false, list => [..list, c]);
         
-        Assert.Equal(a, imTree.GetOrDefaultByValue(key1));
-        Assert.Equal(c, imTree.GetOrDefaultByValue(key2));
+        Assert.Equal([a], imTree.GetOrDefaultByValue(key1));
+        Assert.Equal([b, c], imTree.GetOrDefaultByValue(key2));
         
-        imTree = imTree.UpdateIfExists(key2, b, false);
+        imTree = imTree.UpdateIfExists(key2, [b], false);
         
-        Assert.Equal(a, imTree.GetOrDefaultByValue(key1));
-        Assert.Equal(b, imTree.GetOrDefaultByValue(key2));
+        Assert.Equal([a], imTree.GetOrDefaultByValue(key1));
+        Assert.Equal([b], imTree.GetOrDefaultByValue(key2));
     }
     
     [Fact]
@@ -59,38 +60,38 @@ public void Test_Ref_Collision_Check()
         var a = new A();
         var b = new B();
         var c = new C();
-        var imTree = ImmutableTree<Type, object>.Empty;
-        var tree = new HashTree<Type, object>();
+        var imTree = ImmutableTree<Type, List<object>>.Empty;
+        var tree = new HashTree<Type, List<object>>();
 
-        imTree = imTree.AddOrUpdate(key1, a, true);
-        imTree = imTree.AddOrUpdate(key2, b, true);
-        tree.Add(key1, a);
-        tree.Add(key2, b);
-        
-        Assert.Equal(a, imTree.GetOrDefaultByRef(key1));
-        Assert.Equal(b, imTree.GetOrDefaultByRef(key2));
-        Assert.Equal(a, tree.GetOrDefault(key1));
-        Assert.Equal(b, tree.GetOrDefault(key2));
+        imTree = imTree.AddOrUpdate(key1, [a], true);
+        imTree = imTree.AddOrUpdate(key2, [b], true);
+        tree.Add(key1, [a]);
+        tree.Add(key2, [b]);
+        
+        Assert.Equal([a], imTree.GetOrDefaultByRef(key1));
+        Assert.Equal([b], imTree.GetOrDefaultByRef(key2));
+        Assert.Equal([a], tree.GetOrDefault(key1));
+        Assert.Equal([b], tree.GetOrDefault(key2));
 
-        imTree = imTree.AddOrUpdate(key2, c, true, (_, n) => n);
+        imTree = imTree.AddOrUpdate(key2, [c], true, (list, n) => [..list, ..n]);
         
-        Assert.Equal(a, imTree.GetOrDefaultByRef(key1));
-        Assert.Equal(c, imTree.GetOrDefaultByRef(key2));
+        Assert.Equal([a], imTree.GetOrDefaultByRef(key1));
+        Assert.Equal([b, c], imTree.GetOrDefaultByRef(key2));
 
-        imTree = imTree.AddOrUpdate(key2, b, true, true);
+        imTree = imTree.AddOrUpdate(key2, [b], true, true);
         
-        Assert.Equal(a, imTree.GetOrDefaultByRef(key1));
-        Assert.Equal(b, imTree.GetOrDefaultByRef(key2));
+        Assert.Equal([a], imTree.GetOrDefaultByRef(key1));
+        Assert.Equal([b], imTree.GetOrDefaultByRef(key2));
         
-        imTree = imTree.UpdateIfExists(key2, true, _ => c);
+        imTree = imTree.UpdateIfExists(key2, true, list => [..list, c]);
         
-        Assert.Equal(a, imTree.GetOrDefaultByRef(key1));
-        Assert.Equal(c, imTree.GetOrDefaultByRef(key2));
+        Assert.Equal([a], imTree.GetOrDefaultByRef(key1));
+        Assert.Equal([b, c], imTree.GetOrDefaultByRef(key2));
         
-        imTree = imTree.UpdateIfExists(key2, b, true);
+        imTree = imTree.UpdateIfExists(key2, [b], true);
         
-        Assert.Equal(a, imTree.GetOrDefaultByRef(key1));
-        Assert.Equal(b, imTree.GetOrDefaultByRef(key2));
+        Assert.Equal([a], imTree.GetOrDefaultByRef(key1));
+        Assert.Equal([b], imTree.GetOrDefaultByRef(key2));
     }
     
     [Fact]