diff --git a/src/Avalonia.Controls/TextBox.cs b/src/Avalonia.Controls/TextBox.cs
index 2a8fdd30c7..51a7fe9b7f 100644
--- a/src/Avalonia.Controls/TextBox.cs
+++ b/src/Avalonia.Controls/TextBox.cs
@@ -1017,7 +1017,7 @@ namespace Avalonia.Controls
             }
         }
 
-        public string? RemoveInvalidCharacters(string? text)
+        private string? RemoveInvalidCharacters(string? text)
         {
             if (text is null)
                 return null;