diff --git a/PKHeX.WinForms/Controls/PKM Editor/PKMEditor.cs b/PKHeX.WinForms/Controls/PKM Editor/PKMEditor.cs
index 2b6a39433..15b895db8 100644
--- a/PKHeX.WinForms/Controls/PKM Editor/PKMEditor.cs	
+++ b/PKHeX.WinForms/Controls/PKM Editor/PKMEditor.cs	
@@ -1211,7 +1211,7 @@ private void ReloadMetLocations(GameVersion version, int format)
 
         private void UpdateExtraByteValue(object sender, EventArgs e)
         {
-            if (CB_ExtraBytes.Items.Count == 0 || sender is not MaskedTextBox mtb)
+            if (!FieldsLoaded || CB_ExtraBytes.Items.Count == 0 || sender is not MaskedTextBox mtb)
                 return;
             // Changed Extra Byte's Value
             var value = Util.ToInt32(mtb.Text);