diff --git a/src/Avalonia.Controls/TextBox.cs b/src/Avalonia.Controls/TextBox.cs
index dad2401921..edd268a86a 100644
--- a/src/Avalonia.Controls/TextBox.cs
+++ b/src/Avalonia.Controls/TextBox.cs
@@ -157,6 +157,13 @@ namespace Avalonia.Controls
             }
 
             public bool Equals(UndoRedoState other) => ReferenceEquals(Text, other.Text) || Equals(Text, other.Text);
+
+            public override bool Equals(object obj)
+            {
+                if (ReferenceEquals(null, obj)) return false;
+                if (obj.GetType() != GetType()) return false;
+                return Equals((UndoRedoState)obj);
+            }
         }
 
         private string _text;