--- a/browser/base/content/tab-content.js
+++ b/browser/base/content/tab-content.js
@@ -246,25 +246,42 @@ var AboutReaderListener = {
 
   _articlePromise: null,
 
   init: function() {
     addEventListener("AboutReaderContentLoaded", this, false, true);
     addEventListener("DOMContentLoaded", this, false);
     addEventListener("pageshow", this, false);
     addEventListener("pagehide", this, false);
-    addMessageListener("Reader:ParseDocument", this);
+    addMessageListener("Reader:ToggleReaderMode", this);
     addMessageListener("Reader:PushState", this);
   },
 
   receiveMessage: function(message) {
     switch (message.name) {
-      case "Reader:ParseDocument":
-        this._articlePromise = ReaderMode.parseDocument(content.document).catch(Cu.reportError);
-        content.document.location = "about:reader?url=" + encodeURIComponent(message.data.url);
+      case "Reader:ToggleReaderMode":
+        let url = content.document.location.href;
+        if (!this.isAboutReader) {
+          this._articlePromise = ReaderMode.parseDocument(content.document).catch(Cu.reportError);
+          content.document.location = "about:reader?url=" + encodeURIComponent(url);
+        } else {
+          let originalURL = ReaderMode.getOriginalUrl(url);
+          let webNav = docShell.QueryInterface(Ci.nsIWebNavigation);
+          let sh = webNav.sessionHistory;
+          if (webNav.canGoBack) {
+            let prevEntry = sh.getEntryAtIndex(sh.index - 1, false);
+            let prevURL = prevEntry.URI.spec;
+            if (prevURL && (prevURL == originalURL || !originalURL)) {
+              webNav.goBack();
+              break;
+            }
+          }
+
+          content.document.location = originalURL;
+        }
         break;
 
       case "Reader:PushState":
         this.updateReaderButton(!!(message.data && message.data.isArticle));
         break;
     }
   },
 

--- a/browser/base/content/test/general/browser_bug1124271_readerModePinnedTab.js
+++ b/browser/base/content/test/general/browser_bug1124271_readerModePinnedTab.js
@@ -33,15 +33,15 @@ add_task(function* () {
 
   readerButton.click();
   yield promiseTabLoadEvent(tab);
 
   // Ensure no new tabs are opened when exiting reader mode in a pinned tab
   is(gBrowser.tabs.length, initialTabsCount, "No additional tabs were opened.");
 
   readerButton.click();
-  yield promiseTabLoadEvent(tab);
+  yield BrowserTestUtils.waitForContentEvent(tab.linkedBrowser, "pageshow");
 
   // Ensure no new tabs are opened when exiting reader mode in a pinned tab
   is(gBrowser.tabs.length, initialTabsCount, "No additional tabs were opened.");
 
   gBrowser.removeCurrentTab();
 });

--- a/browser/base/content/test/general/browser_readerMode.js
+++ b/browser/base/content/test/general/browser_readerMode.js
@@ -66,19 +66,21 @@ add_task(function* test_reader_button() 
       gURLBar.focus();
       gURLBar.select();
       goDoCommand("cmd_copy");
     }, resolve, reject);
   });
 
   // Switch page back out of reader mode.
   readerButton.click();
-  yield promiseTabLoadEvent(tab);
+  yield BrowserTestUtils.waitForContentEvent(tab.linkedBrowser, "pageshow");
   is(gBrowser.selectedBrowser.currentURI.spec, url,
-    "Original page loaded after clicking active reader mode button");
+    "Back to the original page after clicking active reader mode button");
+  ok(gBrowser.selectedBrowser.canGoForward,
+    "Moved one step back in the session history.");
 
   // Load a new tab that is NOT reader-able.
   let newTab = gBrowser.selectedTab = gBrowser.addTab();
   yield promiseTabLoadEvent(newTab, "about:robots");
   yield promiseWaitForCondition(() => readerButton.hidden);
   is_element_hidden(readerButton, "Reader mode button is not present on a non-reader-able page");
 
   // Switch back to the original tab to make sure reader mode button is still visible.

--- a/browser/base/content/test/general/head.js
+++ b/browser/base/content/test/general/head.js
@@ -597,18 +597,16 @@ var FullZoomHelper = {
 /**
  * Waits for a load (or custom) event to finish in a given tab. If provided
  * load an uri into the tab.
  *
  * @param tab
  *        The tab to load into.
  * @param [optional] url
  *        The url to load, or the current url.
- * @param [optional] event
- *        The load event type to wait for.  Defaults to "load".
  * @return {Promise} resolved when the event is handled.
  * @resolves to the received event
  * @rejects if a valid load event is not received within a meaningful interval
  */
 function promiseTabLoadEvent(tab, url)
 {
   let deferred = Promise.defer();
   info("Wait tab event: load");

--- a/browser/modules/ReaderParent.jsm
+++ b/browser/modules/ReaderParent.jsm
@@ -128,28 +128,17 @@ var ReaderParent = {
       return;
     }
     this.toggleReaderMode(event);
   },
 
   toggleReaderMode: function(event) {
     let win = event.target.ownerDocument.defaultView;
     let browser = win.gBrowser.selectedBrowser;
-    let url = browser.currentURI.spec;
-
-    if (url.startsWith("about:reader")) {
-      let originalURL = ReaderMode.getOriginalUrl(url);
-      if (!originalURL) {
-        Cu.reportError("Error finding original URL for about:reader URL: " + url);
-      } else {
-        win.openUILinkIn(originalURL, "current", {"allowPinnedTabHostChange": true});
-      }
-    } else {
-      browser.messageManager.sendAsyncMessage("Reader:ParseDocument", { url: url });
-    }
+    browser.messageManager.sendAsyncMessage("Reader:ToggleReaderMode");
   },
 
   /**
    * Shows an info panel from the UITour for Reader Mode.
    *
    * @param browser The <browser> that the tour should be started for.
    */
   showReaderModeInfoPanel(browser) {