diff --git a/extensions/markdown/preview-src/csp.ts b/extensions/markdown/preview-src/csp.ts
index 007e7e30fbb80e1c97a751416590e9a81dbd3a82..a418fad2ab7f9e8aafe934e757699c8dd5c49629 100644
--- a/extensions/markdown/preview-src/csp.ts
+++ b/extensions/markdown/preview-src/csp.ts
@@ -4,6 +4,7 @@
  *--------------------------------------------------------------------------------------------*/
 
 import { getSettings } from './settings';
+import { postCommand } from './messaging';
 
 const strings = JSON.parse(document.getElementById('vscode-markdown-preview-data').getAttribute('data-strings'));
 const settings = getSettings();
@@ -24,14 +25,7 @@ const showCspWarning = () => {
 	notification.setAttribute('role', 'button');
 	notification.setAttribute('aria-label', strings.cspAlertMessageLabel);
 	notification.onclick = () => {
-		window.parent.postMessage({
-			type: 'command',
-			source: settings.source,
-			body: {
-				command: 'markdown.showPreviewSecuritySelector',
-				args: [settings.source]
-			}
-		}, '*');
+		postCommand('markdown.showPreviewSecuritySelector', [settings.source]);
 	};
 	document.body.appendChild(notification);
 };
diff --git a/extensions/markdown/preview-src/index.ts b/extensions/markdown/preview-src/index.ts
index 1311315897d297f833cd771b24ec52a0b416a366..e37a40a86a64b77187ace500ca778cf62e9a7562 100644
--- a/extensions/markdown/preview-src/index.ts
+++ b/extensions/markdown/preview-src/index.ts
@@ -4,7 +4,7 @@
  *--------------------------------------------------------------------------------------------*/
 
 import { getSettings } from './settings';
-
+import { postCommand, postMessage } from './messaging';
 
 // From https://remysharp.com/2010/07/21/throttling-function-calls
 function throttle(fn: (x: any) => any, threshhold: any, scope?: any) {
@@ -37,24 +37,6 @@ function clampLine(line: number) {
 	return clamp(0, settings.lineCount - 1, line);
 }
 
-/**
- * Post a message to the markdown extension
- */
-function postMessage(type: string, body: object) {
-	window.parent.postMessage({
-		type,
-		source: settings.source,
-		body
-	}, '*');
-}
-
-/**
- * Post a command to be executed to the markdown extension
- */
-function postCommand(command: string, args: any[]) {
-	postMessage('command', { command, args });
-}
-
 
 interface CodeLineElement {
 	element: HTMLElement;
diff --git a/extensions/markdown/preview-src/loading.ts b/extensions/markdown/preview-src/loading.ts
index ae4c01f68e48dec4d8699029e2956afd20e0fac3..757eba7b8e631cdfb575c6fc2aa19d0cdf6601ba 100644
--- a/extensions/markdown/preview-src/loading.ts
+++ b/extensions/markdown/preview-src/loading.ts
@@ -3,6 +3,7 @@
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 import { getSettings } from './settings';
+import { postCommand } from './messaging';
 
 const unloadedStyles: string[] = [];
 
@@ -25,12 +26,5 @@ window.addEventListener('load', () => {
 	if (!unloadedStyles.length) {
 		return;
 	}
-	window.parent.postMessage({
-		type: 'command',
-		source: settings.source,
-		body: {
-			command: '_markdown.onPreviewStyleLoadError',
-			args: [unloadedStyles]
-		}
-	}, '*');
+	postCommand('_markdown.onPreviewStyleLoadError', [unloadedStyles]);
 });
\ No newline at end of file
diff --git a/extensions/markdown/preview-src/messaging.ts b/extensions/markdown/preview-src/messaging.ts
new file mode 100644
index 0000000000000000000000000000000000000000..10571ff28db6147e4211ccfd30a2d511638fd114
--- /dev/null
+++ b/extensions/markdown/preview-src/messaging.ts
@@ -0,0 +1,24 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { getSettings } from './settings';
+
+/**
+ * Post a message to the markdown extension
+ */
+export function postMessage(type: string, body: object) {
+	window.parent.postMessage({
+		type,
+		source: getSettings().source,
+		body
+	}, '*');
+}
+
+/**
+ * Post a command to be executed to the markdown extension
+ */
+export function postCommand(command: string, args: any[]) {
+	postMessage('command', { command, args });
+}