--- a/browser/components/sessionstore/src/SessionStore.jsm
+++ b/browser/components/sessionstore/src/SessionStore.jsm
@@ -3723,16 +3723,19 @@ let SessionStoreInternal = {
       return;
     }
 
 #ifdef MOZ_PER_WINDOW_PRIVATE_BROWSING
     // Forget about private windows.
     for (let i = oState.windows.length - 1; i >= 0; i--) {
       if (oState.windows[i].isPrivate) {
         oState.windows.splice(i, 1);
+        if (oState.selectedWindow >= i) {
+          oState.selectedWindow--;
+        }
       }
     }
     for (let i = oState._closedWindows.length - 1; i >= 0; i--) {
       if (oState._closedWindows[i].isPrivate) {
         oState._closedWindows.splice(i, 1);
       }
     }
 #endif

--- a/browser/components/sessionstore/test/Makefile.in
+++ b/browser/components/sessionstore/test/Makefile.in
@@ -136,16 +136,17 @@ MOCHITEST_BROWSER_FILES = \
 	$(filter disabled-for-intermittent-failures--bug-766044, browser_459906_sample.html) \
 	$(filter disabled-for-intermittent-failures--bug-765389, browser_461743_sample.html) \
 	$(NULL)
 
 ifdef MOZ_PER_WINDOW_PRIVATE_BROWSING
 MOCHITEST_BROWSER_FILES += \
 	browser_354894_perwindowpb.js \
 	browser_394759_perwindowpb.js \
+	browser_819510_perwindowpb.js \
 	$(NULL)
 else
 MOCHITEST_BROWSER_FILES += \
 	browser_248970_a.js \
 	browser_248970_b.js \
 	browser_248970_b_perwindowpb.js \
 	browser_354894.js \
 	browser_394759_privatebrowsing.js \

new file mode 100644
--- /dev/null
+++ b/browser/components/sessionstore/test/browser_819510_perwindowpb.js
@@ -0,0 +1,181 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const originalState = ss.getBrowserState();
+
+/** Private Browsing Test for Bug 819510 **/
+function test() {
+  waitForExplicitFinish();
+
+  registerCleanupFunction(function() {
+    Services.prefs.clearUserPref("browser.sessionstore.interval");
+    ss.setBrowserState(originalState);
+  });
+
+  runNextTest();
+}
+
+let tests = [test_1, test_2, test_3 ];
+
+const testState = {
+  windows: [{
+    tabs: [
+      { entries: [{ url: "about:blank" }] },
+    ]
+  }]
+};
+
+function runNextTest() {
+  // Set an empty state
+  closeAllButPrimaryWindow();
+
+  // Run the next test, or finish
+  if (tests.length) {
+    let currentTest = tests.shift();
+    waitForBrowserState(testState, currentTest);
+  } else {
+    Services.prefs.clearUserPref("browser.sessionstore.interval");
+    ss.setBrowserState(originalState);
+    finish();
+  }
+}
+
+// Test opening default mochitest-normal-private-normal-private windows
+// (saving the state with last window being private)
+function test_1() {
+  testOnWindow(false, function(aWindow) {
+    aWindow.gBrowser.addTab("http://www.example.com/1");
+    testOnWindow(true, function(aWindow) {
+      aWindow.gBrowser.addTab("http://www.example.com/2");
+      testOnWindow(false, function(aWindow) {
+        aWindow.gBrowser.addTab("http://www.example.com/3");
+        testOnWindow(true, function(aWindow) {
+          aWindow.gBrowser.addTab("http://www.example.com/4");
+
+          let curState = JSON.parse(ss.getBrowserState());
+          is (curState.windows.length, 5, "Browser has opened 5 windows");
+          is (curState.windows[2].isPrivate, true, "Window is private");
+          is (curState.windows[4].isPrivate, true, "Last window is private");
+          is (curState.selectedWindow, 5, "Last window opened is the one selected");
+
+          forceWriteState(function(state) {
+            is(state.windows.length, 3,
+               "sessionstore state: 3 windows in data being written to disk");
+            is (state.selectedWindow, 3,
+               "Selected window is updated to match one of the saved windows");
+            state.windows.forEach(function(win) {
+              is(!win.isPrivate, true, "Saved window is not private");
+            });
+            is(state._closedWindows.length, 0,
+               "sessionstore state: no closed windows in data being written to disk");
+            runNextTest();
+          });
+        });
+      });
+    });
+  });
+}
+
+// Test opening default mochitest window + 2 private windows
+function test_2() {
+  testOnWindow(true, function(aWindow) {
+    aWindow.gBrowser.addTab("http://www.example.com/1");
+    testOnWindow(true, function(aWindow) {
+      aWindow.gBrowser.addTab("http://www.example.com/2");
+
+      let curState = JSON.parse(ss.getBrowserState());
+      is (curState.windows.length, 3, "Browser has opened 3 windows");
+      is (curState.windows[1].isPrivate, true, "Window 1 is private");
+      is (curState.windows[2].isPrivate, true, "Window 2 is private");
+      is (curState.selectedWindow, 3, "Last window opened is the one selected");
+
+      forceWriteState(function(state) {
+        is(state.windows.length, 1,
+           "sessionstore state: 1 windows in data being writted to disk");
+        is (state.selectedWindow, 1,
+           "Selected window is updated to match one of the saved windows");
+        is(state._closedWindows.length, 0,
+           "sessionstore state: no closed windows in data being writted to disk");
+        runNextTest();
+      });
+    });
+  });
+}
+
+// Test opening default-normal-private-normal windows and closing a normal window
+function test_3() {
+  testOnWindow(false, function(normalWindow) {
+    let tab = normalWindow.gBrowser.addTab("http://www.example.com/1");
+    whenBrowserLoaded(tab.linkedBrowser, function() {
+      testOnWindow(true, function(aWindow) {
+        aWindow.gBrowser.addTab("http://www.example.com/2");
+        testOnWindow(false, function(aWindow) {
+          aWindow.gBrowser.addTab("http://www.example.com/3");
+
+          let curState = JSON.parse(ss.getBrowserState());
+          is (curState.windows.length, 4, "Browser has opened 4 windows");
+          is (curState.windows[2].isPrivate, true, "Window 2 is private");
+          is (curState.selectedWindow, 4, "Last window opened is the one selected");
+
+          waitForWindowClose(normalWindow, function() {
+            forceWriteState(function(state) {
+              is(state.windows.length, 2,
+                 "sessionstore state: 2 windows in data being writted to disk");
+              is(state.selectedWindow, 2,
+                 "Selected window is updated to match one of the saved windows");
+              state.windows.forEach(function(win) {
+                is(!win.isPrivate, true, "Saved window is not private");
+              });
+              is(state._closedWindows.length, 1,
+                 "sessionstore state: 1 closed window in data being writted to disk");
+              state._closedWindows.forEach(function(win) {
+                is(!win.isPrivate, true, "Closed window is not private");
+              });
+              runNextTest();
+            });
+          });
+        });
+      });
+    });
+  });
+}
+
+function waitForWindowClose(aWin, aCallback) {
+  Services.obs.addObserver(function observe(aSubject, aTopic, aData) {
+    if (aTopic == "domwindowclosed" && aWin == aSubject) {
+      Services.obs.removeObserver(observe, aTopic);
+      checkWindowIsClosed(aWin, aCallback);
+    }
+  }, "domwindowclosed", false);
+  aWin.close();
+}
+
+function checkWindowIsClosed(aWin, aCallback) {
+  if (aWin.closed) {
+    info("Window is closed");
+    executeSoon(aCallback);
+  } else {
+    executeSoon(function() {
+      checkWindowIsClosed(aWin, aCallback);
+    });
+  }
+}
+
+function forceWriteState(aCallback) {
+  Services.obs.addObserver(function observe(aSubject, aTopic, aData) {
+    if (aTopic == "sessionstore-state-write") {
+      Services.obs.removeObserver(observe, aTopic);
+      aSubject.QueryInterface(Ci.nsISupportsString);
+      aCallback(JSON.parse(aSubject.data));
+    }
+  }, "sessionstore-state-write", false);
+  Services.prefs.setIntPref("browser.sessionstore.interval", 0);
+}
+
+function testOnWindow(aIsPrivate, aCallback) {
+  let win = OpenBrowserWindow({private: aIsPrivate});
+  win.addEventListener("load", function onLoad() {
+    win.removeEventListener("load", onLoad, false);
+    executeSoon(function() { aCallback(win); });
+  }, false);
+}