diff --git a/README.md b/README.md
index edd0155..bdb7dd3 100644
--- a/README.md
+++ b/README.md
@@ -50,12 +50,14 @@ The `.yaml` format structure is as follows:
 
 * Root [dict]
    * `Errors` [list of dict]: Specific error codes
-      * `printers` (optional) [list of string]: same as root-level printer filter
       * `code` [string]: Error code in the format `XXYZZ`
          * Leave `XX` as `XX`, the code applies to multiple printers.
          * For example `XX101`
+      * `printers` (optional) [list of string]: same as root-level printer filter
       * `title` [string]: Error message title
       * `text` [string]: Error message string
       * `id` [string]: Error identifier used for referencing the error in the code
          * For example `BED_MINTEMP_ERROR`
+      * `gui_layout` [string]: For warning or error
+         * For example `"warning_dialog"` or `"red_screen"`
       * `approved` [bool]: Not really good for anything
diff --git a/yaml/mmu-error-codes.yaml b/yaml/mmu-error-codes.yaml
index 8cca02d..8f61f39 100644
--- a/yaml/mmu-error-codes.yaml
+++ b/yaml/mmu-error-codes.yaml
@@ -345,7 +345,6 @@ Errors:
 - code: "04306"
   title: "MMU MCU ERROR"
   text: "MMU detected a power-related issue. Check the wiring and connectors. If the issue persists, contact support."
-  text_short: "More details online."
   action: [ResetMMU]
   id: "MCU_POWER_ERROR"
   approved: true
@@ -447,6 +446,16 @@ Errors:
   type: USER_ACTION
   gui_layout: "mmu_dialog"
 
+- code: "04508"
+  title: "FILAMENT CHANGE"
+  text: "Change filament. Eject filament then load new filament into the MMU."
+  text_short: "M600 Filament Change. Load a new filament or eject the old one."
+  action: [Eject,Load]
+  id: "FILAMENT_CHANGE"
+  approved: true
+  type: USER_ACTION
+  gui_layout: "mmu_dialog"
+
 - code: "04900"
   title: "UNKNOWN ERROR"
   text: "Unexpected error occurred."