diff --git a/browser/components/sessionstore/content/content-sessionStore.js b/browser/components/sessionstore/content/content-sessionStore.js
index 74da0a69bcb4..881fd18142fc 100644
--- a/browser/components/sessionstore/content/content-sessionStore.js
+++ b/browser/components/sessionstore/content/content-sessionStore.js
@@ -308,6 +308,30 @@ let SessionStorageListener = {
                                          Ci.nsISupportsWeakReference])
 };
 
+/**
+ * Listen for changes to the privacy status of the tab.
+ * By definition, tabs start in non-private mode.
+ *
+ * Causes a SessionStore:update message to be sent for
+ * field "isPrivate". This message contains
+ *  |true| if the tab is now private
+ *  |null| if the tab is now public - the field is therefore
+ *  not saved.
+ */
+let PrivacyListener = {
+  init: function() {
+    docShell.addWeakPrivacyTransitionObserver(this);
+  },
+
+  // Ci.nsIPrivacyTransitionObserver
+  privateModeChanged: function(enabled) {
+    MessageQueue.push("isPrivate", () => enabled || null);
+  },
+
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIPrivacyTransitionObserver,
+                                         Ci.nsISupportsWeakReference])
+};
+
 /**
  * A message queue that takes collected data and will take care of sending it
  * to the chrome process. It allows flushing using synchronous messages and
@@ -461,3 +485,4 @@ ProgressListener.init();
 PageStyleListener.init();
 SessionStorageListener.init();
 DocShellCapabilitiesListener.init();
+PrivacyListener.init();
diff --git a/browser/components/sessionstore/src/SessionSaver.jsm b/browser/components/sessionstore/src/SessionSaver.jsm
index 7d93bd220d0c..f04545810e42 100644
--- a/browser/components/sessionstore/src/SessionSaver.jsm
+++ b/browser/components/sessionstore/src/SessionSaver.jsm
@@ -192,12 +192,24 @@ let SessionSaverInternal = {
     stopWatchStart("COLLECT_DATA_MS", "COLLECT_DATA_LONGEST_OP_MS");
     let state = SessionStore.getCurrentState(forceUpdateAllWindows);
 
-    // Forget about private windows.
+    // Forget about private windows and tabs.
     for (let i = state.windows.length - 1; i >= 0; i--) {
-      if (state.windows[i].isPrivate) {
-        state.windows.splice(i, 1);
-        if (state.selectedWindow >= i) {
-          state.selectedWindow--;
+      let win = state.windows[i];
+      if (win.isPrivate || false) { // The whole window is private, remove it
+         state.windows.splice(i, 1);
+         if (state.selectedWindow >= i) {
+           state.selectedWindow--;
+         }
+        continue;
+      }
+      // The window is not private, but its tabs still might
+      for (let j = win.tabs.length - 1; j >= 0 ; --j) {
+        let tab = win.tabs[j];
+        if (tab.isPrivate || false) {
+          win.tabs.splice(j, 1);
+          if (win.selected >= j) {
+            win.selected--;
+          }
         }
       }
     }
@@ -209,6 +221,10 @@ let SessionSaverInternal = {
       }
     }
 
+    // Note that closed private tabs are never stored (see
+    // SessionStoreInternal.onTabClose), so we do not need to remove
+    // them.
+
     // Make sure that we keep the previous session if we started with a single
     // private window and no non-private windows have been opened, yet.
     if (state.deferredInitialState) {
diff --git a/browser/components/sessionstore/src/SessionStore.jsm b/browser/components/sessionstore/src/SessionStore.jsm
index a5497b485255..cd906c93c85f 100644
--- a/browser/components/sessionstore/src/SessionStore.jsm
+++ b/browser/components/sessionstore/src/SessionStore.jsm
@@ -1320,6 +1320,11 @@ let SessionStoreInternal = {
     // Get the latest data for this tab (generally, from the cache)
     let tabState = TabState.collectSync(aTab);
 
+    // Don't save private tabs
+    if (tabState.isPrivate || false) {
+      return;
+    }
+
     // store closed-tab data for undo
     if (this._shouldSaveTabState(tabState)) {
       let tabTitle = aTab.label;
diff --git a/browser/components/sessionstore/test/browser.ini b/browser/components/sessionstore/test/browser.ini
index 6ed3b4915046..cdee1041720e 100644
--- a/browser/components/sessionstore/test/browser.ini
+++ b/browser/components/sessionstore/test/browser.ini
@@ -58,6 +58,7 @@ support-files =
 [browser_input.js]
 [browser_pageshow.js]
 [browser_pageStyle.js]
+[browser_privatetabs.js]
 [browser_sessionStorage.js]
 [browser_swapDocShells.js]
 [browser_tabStateCache.js]
diff --git a/browser/components/sessionstore/test/browser_privatetabs.js b/browser/components/sessionstore/test/browser_privatetabs.js
new file mode 100644
index 000000000000..8eb5d61e104b
--- /dev/null
+++ b/browser/components/sessionstore/test/browser_privatetabs.js
@@ -0,0 +1,67 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+let Imports = {};
+Cu.import("resource://gre/modules/Task.jsm", Imports);
+Cu.import("resource://gre/modules/Promise.jsm", Imports);
+let {Promise, Task} = Imports;
+
+add_task(function cleanup() {
+  while (ss.getClosedTabCount(window)) {
+    ss.forgetClosedTab(window, 0);
+  }
+});
+
+add_task(function() {
+  let URL_PUBLIC = "http://example.com/public/" + Math.random();
+  let URL_PRIVATE = "http://example.com/private/" + Math.random();
+  let tab1, tab2;
+  try {
+    // Setup a public tab and a private tab
+    info("Setting up public tab");
+    tab1 = gBrowser.addTab(URL_PUBLIC);
+    yield promiseBrowserLoaded(tab1.linkedBrowser);
+
+    info("Setting up private tab");
+    tab2 = gBrowser.addTab();
+    yield promiseBrowserLoaded(tab2.linkedBrowser);
+    setUsePrivateBrowsing(tab2.linkedBrowser, true);
+    tab2.linkedBrowser.loadURI(URL_PRIVATE);
+    yield promiseBrowserLoaded(tab2.linkedBrowser);
+
+    info("Flush to make sure chrome received all data.");
+    SyncHandlers.get(tab2.linkedBrowser).flush();
+
+    info("Checking out state");
+    yield forceSaveState();
+    let state = new TextDecoder().decode((yield OS.File.read(OS.Path.join(OS.Constants.Path.profileDir, "sessionstore.js"))));
+    info("State: " + state);
+    // Ensure that sessionstore.js only knows about the public tab
+    ok(state.indexOf(URL_PUBLIC) != -1, "State contains public tab");
+    ok(state.indexOf(URL_PRIVATE) == -1, "State does not contain private tab");
+
+    // Ensure that we can close and undo close the public tab but not the private tab
+    gBrowser.removeTab(tab2);
+    tab2 = null;
+
+    gBrowser.removeTab(tab1);
+    tab1 = null;
+
+    tab1 = ss.undoCloseTab(window, 0);
+    ok(true, "Public tab supports undo close");
+
+    is(ss.getClosedTabCount(window), 0, "Private tab does not support undo close");
+
+  } finally {
+    if (tab1) {
+      gBrowser.removeTab(tab1);
+    }
+    if (tab2) {
+      gBrowser.removeTab(tab2);
+    }
+  }
+});
+
+function setUsePrivateBrowsing(browser, val) {
+  return sendMessage(browser, "ss-test:setUsePrivateBrowsing", val);
+}
diff --git a/browser/components/sessionstore/test/content.js b/browser/components/sessionstore/test/content.js
index e839d1375651..ac70f745a641 100644
--- a/browser/components/sessionstore/test/content.js
+++ b/browser/components/sessionstore/test/content.js
@@ -50,3 +50,10 @@ addMessageListener("ss-test:setAuthorStyleDisabled", function (msg) {
   markupDocumentViewer.authorStyleDisabled = msg.data;
   sendSyncMessage("ss-test:setAuthorStyleDisabled");
 });
+
+addMessageListener("ss-test:setUsePrivateBrowsing", function (msg) {
+  let loadContext =
+    docShell.QueryInterface(Ci.nsILoadContext);
+  loadContext.usePrivateBrowsing = msg.data;
+  sendSyncMessage("ss-test:setAuthorStyleDisabled");
+});