diff --git a/src/components/structures/RoomView.tsx b/src/components/structures/RoomView.tsx
index e6eca5023f..645ceee56d 100644
--- a/src/components/structures/RoomView.tsx
+++ b/src/components/structures/RoomView.tsx
@@ -2097,13 +2097,15 @@ export class RoomView extends React.Component<IRoomProps, IRoomState> {
             }
         }
 
+        const roomHeaderType = SettingsStore.getValue("feature_new_room_decoration_ui") ? "new" : "legacy";
+
         if (!this.state.room) {
             const loading = !this.state.matrixClientIsReady || this.state.roomLoading || this.state.peekLoading;
             if (loading) {
                 // Assume preview loading if we don't have a ready client or a room ID (still resolving the alias)
                 const previewLoading = !this.state.matrixClientIsReady || !this.state.roomId || this.state.peekLoading;
                 return (
-                    <div className="mx_RoomView">
+                    <div className="mx_RoomView" data-room-header={roomHeaderType}>
                         <ErrorBoundary>
                             <RoomPreviewBar
                                 canPreview={false}
@@ -2128,7 +2130,7 @@ export class RoomView extends React.Component<IRoomProps, IRoomState> {
                 // We've got to this room by following a link, possibly a third party invite.
                 const roomAlias = this.state.roomAlias;
                 return (
-                    <div className="mx_RoomView">
+                    <div className="mx_RoomView" data-room-header={roomHeaderType}>
                         <ErrorBoundary>
                             <RoomPreviewBar
                                 onJoinClick={this.onJoinButtonClicked}
@@ -2201,7 +2203,7 @@ export class RoomView extends React.Component<IRoomProps, IRoomState> {
 
                 // We have a regular invite for this room.
                 return (
-                    <div className="mx_RoomView">
+                    <div className="mx_RoomView" data-room-header={roomHeaderType}>
                         <ErrorBoundary>
                             <RoomPreviewBar
                                 onJoinClick={this.onJoinButtonClicked}
@@ -2222,7 +2224,7 @@ export class RoomView extends React.Component<IRoomProps, IRoomState> {
 
         if (this.state.canAskToJoin && ["knock", "leave"].includes(myMembership)) {
             return (
-                <div className="mx_RoomView">
+                <div className="mx_RoomView" data-room-header={roomHeaderType}>
                     <ErrorBoundary>
                         <RoomPreviewBar
                             room={this.state.room}
@@ -2326,7 +2328,11 @@ export class RoomView extends React.Component<IRoomProps, IRoomState> {
                 />
             );
             if (!this.state.canPeek && !this.state.room?.isSpaceRoom()) {
-                return <div className="mx_RoomView">{previewBar}</div>;
+                return (
+                    <div className="mx_RoomView" data-room-header={roomHeaderType}>
+                        {previewBar}
+                    </div>
+                );
             }
         } else if (hiddenHighlightCount > 0) {
             aux = (
@@ -2571,7 +2577,12 @@ export class RoomView extends React.Component<IRoomProps, IRoomState> {
 
         return (
             <RoomContext.Provider value={this.state}>
-                <main className={mainClasses} ref={this.roomView} onKeyDown={this.onReactKeyDown}>
+                <main
+                    className={mainClasses}
+                    ref={this.roomView}
+                    onKeyDown={this.onReactKeyDown}
+                    data-room-header={roomHeaderType}
+                >
                     {showChatEffects && this.roomView.current && (
                         <EffectsOverlay roomWidth={this.roomView.current.offsetWidth} />
                     )}
diff --git a/test/components/structures/__snapshots__/RoomView-test.tsx.snap b/test/components/structures/__snapshots__/RoomView-test.tsx.snap
index 9fe61c5e6c..a3a2eaea61 100644
--- a/test/components/structures/__snapshots__/RoomView-test.tsx.snap
+++ b/test/components/structures/__snapshots__/RoomView-test.tsx.snap
@@ -736,6 +736,7 @@ exports[`RoomView should show error view if failed to look up room alias 1`] = `
 <DocumentFragment>
   <div
     class="mx_RoomView"
+    data-room-header="legacy"
   >
     <div
       class="mx_RoomPreviewBar dark-panel mx_RoomPreviewBar_RoomNotFound mx_RoomPreviewBar_dialog"