diff --git a/arduino-ide-extension/src/browser/theia/core/application-shell.ts b/arduino-ide-extension/src/browser/theia/core/application-shell.ts
index d8767008..2e9e8c39 100644
--- a/arduino-ide-extension/src/browser/theia/core/application-shell.ts
+++ b/arduino-ide-extension/src/browser/theia/core/application-shell.ts
@@ -2,10 +2,11 @@
 import { injectable, inject } from 'inversify';
 import { EditorWidget } from '@theia/editor/lib/browser';
 import { CommandService } from '@theia/core/lib/common/command';
-import { PreferencesWidget } from '@theia/preferences/lib/browser/views/preference-widget';
 import { ApplicationShell as TheiaApplicationShell, Widget } from '@theia/core/lib/browser';
+import { Sketch } from '../../../common/protocol';
 import { EditorMode } from '../../editor-mode';
 import { SaveAsSketch } from '../../contributions/save-as-sketch';
+import { SketchesServiceClientImpl } from '../../../common/protocol/sketches-service-client-impl';
 
 @injectable()
 export class ApplicationShell extends TheiaApplicationShell {
@@ -16,26 +17,33 @@ export class ApplicationShell extends TheiaApplicationShell {
     @inject(CommandService)
     protected readonly commandService: CommandService;
 
-    protected track(widget: Widget): void {
-        super.track(widget);
-        if (!this.editorMode.proMode) {
-            if (widget instanceof EditorWidget) {
-                // Always allow closing the whitelisted files.
-                // TODO: It would be better to blacklist the sketch files only.
-                if (['tasks.json',
-                    'launch.json',
-                    'settings.json',
-                    'arduino-cli.yaml'].some(fileName => widget.editor.uri.toString().endsWith(fileName))) {
-                    return;
-                }
-            }
-            if (widget instanceof PreferencesWidget) {
-                return;
-            }
-            widget.title.closable = false;
-        }
+    @inject(SketchesServiceClientImpl)
+    protected readonly sketchesServiceClient: SketchesServiceClientImpl;
+
+    protected sketch?: Sketch;
+
+    async addWidget(widget: Widget, options: Readonly<TheiaApplicationShell.WidgetOptions> = {}): Promise<void> {
+        // Get the current sketch before adding a widget. This wil trigger an update.
+        this.sketch = await this.sketchesServiceClient.currentSketch();
+        super.addWidget(widget, options);
     }
 
+    async setLayoutData(layoutData: TheiaApplicationShell.LayoutData): Promise<void> {
+        // I could not find other ways to get sketch in async fashion for sync `track`.
+        this.sketch = await this.sketchesServiceClient.currentSketch();
+        super.setLayoutData(layoutData);
+    }
+
+    track(widget: Widget): void {
+        if (!this.editorMode.proMode && this.sketch && widget instanceof EditorWidget) {
+            if (Sketch.isInSketch(widget.editor.uri, this.sketch)) {
+                widget.title.closable = false;
+            }
+        }
+        super.track(widget);
+    }
+
+
     async saveAll(): Promise<void> {
         await super.saveAll();
         await this.commandService.executeCommand(SaveAsSketch.Commands.SAVE_AS_SKETCH.id, { execOnlyIfTemp: true, openAfterMove: true });
diff --git a/arduino-ide-extension/src/common/protocol/sketches-service.ts b/arduino-ide-extension/src/common/protocol/sketches-service.ts
index 1ceac6d2..8b8cbefe 100644
--- a/arduino-ide-extension/src/common/protocol/sketches-service.ts
+++ b/arduino-ide-extension/src/common/protocol/sketches-service.ts
@@ -1,3 +1,5 @@
+import URI from '@theia/core/lib/common/uri';
+
 export const SketchesServicePath = '/services/sketches-service';
 export const SketchesService = Symbol('SketchesService');
 export interface SketchesService {
@@ -60,9 +62,9 @@ export namespace Sketch {
         export const ADDITIONAL = ['.h', '.c', '.hpp', '.hh', '.cpp', '.s'];
         export const ALL = Array.from(new Set([...MAIN, ...SOURCE, ...ADDITIONAL]));
     }
-    export function isInSketch(uri: string, sketch: Sketch): boolean {
+    export function isInSketch(uri: string | URI, sketch: Sketch): boolean {
         const { mainFileUri, otherSketchFileUris, additionalFileUris } = sketch;
-        return [mainFileUri, ...otherSketchFileUris, additionalFileUris].indexOf(uri) !== -1;
+        return [mainFileUri, ...otherSketchFileUris, additionalFileUris].indexOf(uri.toString()) !== -1;
     }
 }