diff --git a/extensions/markdown/preview-src/loading.ts b/extensions/markdown/preview-src/loading.ts
index f60cdf226d8d80fb71be44094883c91aa70ac604..3469255877480082dfa3224967bc2c53562960af 100644
--- a/extensions/markdown/preview-src/loading.ts
+++ b/extensions/markdown/preview-src/loading.ts
@@ -4,24 +4,28 @@
  *--------------------------------------------------------------------------------------------*/
 import { postCommand } from './messaging';
 
-const unloadedStyles: string[] = [];
+export class StyleLoadingMonitor {
+	private unloadedStyles: string[] = [];
 
-const onStyleLoadError = (event: any) => {
-	const source = event.target.dataset.source;
-	unloadedStyles.push(source);
-};
+	constructor() {
+		const onStyleLoadError = (event: any) => {
+			const source = event.target.dataset.source;
+			this.unloadedStyles.push(source);
+		};
 
-window.addEventListener('DOMContentLoaded', () => {
-	for (const link of document.getElementsByClassName('code-user-style') as HTMLCollectionOf<HTMLElement>) {
-		if (link.dataset.source) {
-			link.onerror = onStyleLoadError;
-		}
-	}
-});
+		window.addEventListener('DOMContentLoaded', () => {
+			for (const link of document.getElementsByClassName('code-user-style') as HTMLCollectionOf<HTMLElement>) {
+				if (link.dataset.source) {
+					link.onerror = onStyleLoadError;
+				}
+			}
+		});
 
-window.addEventListener('load', () => {
-	if (!unloadedStyles.length) {
-		return;
+		window.addEventListener('load', () => {
+			if (!this.unloadedStyles.length) {
+				return;
+			}
+			postCommand('_markdown.onPreviewStyleLoadError', [this.unloadedStyles]);
+		});
 	}
-	postCommand('_markdown.onPreviewStyleLoadError', [unloadedStyles]);
-});
\ No newline at end of file
+}
\ No newline at end of file
diff --git a/extensions/markdown/preview-src/pre.ts b/extensions/markdown/preview-src/pre.ts
index bf5ba852591ddb3aea803cf14e4d7b61ac5243a5..c9fd0ec5b35123cb934f3ac521e0e3bef3e855d5 100644
--- a/extensions/markdown/preview-src/pre.ts
+++ b/extensions/markdown/preview-src/pre.ts
@@ -3,8 +3,11 @@
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 
-import './loading';
 import { CspAlerter } from './csp';
+import { StyleLoadingMonitor } from './loading';
 
 // tslint:disable-next-line:no-unused-expression
-new CspAlerter();
\ No newline at end of file
+new CspAlerter();
+
+// tslint:disable-next-line:no-unused-expression
+new StyleLoadingMonitor();
\ No newline at end of file