diff --git a/src/chrome/backgroundscript.js b/src/chrome/backgroundscript.js
index 9c1c4372..de66174d 100644
--- a/src/chrome/backgroundscript.js
+++ b/src/chrome/backgroundscript.js
@@ -147,6 +147,15 @@ chrome.runtime.onMessage.addListener(function(request, sender, responseCallback)
   }
 });
 
+// Add listener for cross-extension messaging. (See https://developer.chrome.com/extensions/messaging#external)
+chrome.runtime.onMessageExternal.addListener(function(request) {
+  if (request && request.action === 'toggle-markdown') {
+    chrome.tabs.query({ active: true, currentWindow: true }, function(tabs) {
+      var tab = tabs[0];
+      chrome.tabs.sendMessage(tab.id, {action: 'message-external', });
+    });
+  }
+});
 // Add the browserAction (the button in the browser toolbar) listener.
 chrome.browserAction.onClicked.addListener(function(tab) {
   chrome.tabs.sendMessage(tab.id, {action: 'button-click', });
diff --git a/src/chrome/contentscript.js b/src/chrome/contentscript.js
index 0924b233..c6504147 100644
--- a/src/chrome/contentscript.js
+++ b/src/chrome/contentscript.js
@@ -21,7 +21,8 @@ function requestHandler(request, sender, sendResponse) {
 
   if (request && (request.action === 'context-click' ||
                   request.action === 'hotkey' ||
-                  request.action === 'button-click')) {
+                  request.action === 'button-click' ||
+                  request.action === 'message-external')) {
 
     // Check if the focused element is a valid render target
     focusedElem = markdownHere.findFocusedElem(window.document);