diff --git a/Source/Engine/UI/GUI/Common/TextBoxBase.cs b/Source/Engine/UI/GUI/Common/TextBoxBase.cs
index 201e91c61..491fbcd94 100644
--- a/Source/Engine/UI/GUI/Common/TextBoxBase.cs
+++ b/Source/Engine/UI/GUI/Common/TextBoxBase.cs
@@ -42,6 +42,7 @@ namespace FlaxEngine.GUI
             '\\',
             '>',
             '<',
+            '=',
         };
 
         /// <summary>