--- a/mobile/android/base/java/org/mozilla/gecko/GeckoApp.java
+++ b/mobile/android/base/java/org/mozilla/gecko/GeckoApp.java
@@ -80,16 +80,17 @@ import android.provider.MediaStore.Image
 import android.support.annotation.NonNull;
 import android.support.annotation.WorkerThread;
 import android.support.design.widget.Snackbar;
 import android.text.TextUtils;
 import android.util.AttributeSet;
 import android.util.Base64;
 import android.util.Log;
 import android.util.SparseBooleanArray;
+import android.util.SparseIntArray;
 import android.view.Gravity;
 import android.view.KeyEvent;
 import android.view.Menu;
 import android.view.MenuInflater;
 import android.view.MenuItem;
 import android.view.MotionEvent;
 import android.view.OrientationEventListener;
 import android.view.SurfaceView;
@@ -214,26 +215,34 @@ public abstract class GeckoApp
         private JSONArray tabs;
         private JSONObject windowObject;
         private boolean isExternalURL;
 
         private boolean selectNextTab;
         private boolean tabsWereSkipped;
         private boolean tabsWereProcessed;
 
+        private SparseIntArray tabIdMap;
+
         public LastSessionParser(JSONArray tabs, JSONObject windowObject, boolean isExternalURL) {
             this.tabs = tabs;
             this.windowObject = windowObject;
             this.isExternalURL = isExternalURL;
+
+            tabIdMap = new SparseIntArray();
         }
 
         public boolean allTabsSkipped() {
             return tabsWereSkipped && !tabsWereProcessed;
         }
 
+        public int getNewTabId(int oldTabId) {
+            return tabIdMap.get(oldTabId, -1);
+        }
+
         @Override
         public void onTabRead(final SessionTab sessionTab) {
             if (sessionTab.isAboutHomeWithoutHistory()) {
                 // This is a tab pointing to about:home with no history. We won't restore
                 // this tab. If we end up restoring no tabs then the browser will decide
                 // whether it needs to open about:home or a different 'homepage'. If we'd
                 // always restore about:home only tabs then we'd never open the homepage.
                 // See bug 1261008.
@@ -273,27 +282,58 @@ public abstract class GeckoApp
             ThreadUtils.postToUiThread(new Runnable() {
                 @Override
                 public void run() {
                     tab.updateTitle(sessionTab.getTitle());
                 }
             });
 
             try {
-                tabObject.put("tabId", tab.getId());
+                int oldTabId = tabObject.optInt("tabId", -1);
+                int newTabId = tab.getId();
+                tabObject.put("tabId", newTabId);
+                if  (oldTabId >= 0) {
+                    tabIdMap.put(oldTabId, newTabId);
+                }
             } catch (JSONException e) {
                 Log.e(LOGTAG, "JSON error", e);
             }
             tabs.put(tabObject);
         }
 
         @Override
         public void onClosedTabsRead(final JSONArray closedTabData) throws JSONException {
             windowObject.put("closedTabs", closedTabData);
         }
+
+        /**
+         * Updates stored parent tab IDs in the session store data to match the new tab IDs
+         * that have been allocated during startup session restore.
+         *
+         * @param tabData A JSONArray containg stored session store tabs.
+         */
+        public void updateParentId(final JSONArray tabData) {
+            if (tabData == null) {
+                return;
+            }
+
+            for (int i = 0; i < tabData.length(); i++) {
+                try {
+                    JSONObject tabObject = tabData.getJSONObject(i);
+
+                    int parentId = tabObject.getInt("parentId");
+                    int newParentId = getNewTabId(parentId);
+
+                    tabObject.put("parentId", newParentId);
+                } catch (JSONException ex) {
+                    // Tabs are not guaranteed to have a parentId,
+                    // so just skip the tab and try the next one.
+                }
+            }
+        }
     };
 
     protected boolean mInitialized;
     protected boolean mWindowFocusInitialized;
     private Telemetry.Timer mJavaUiStartupTimer;
     private Telemetry.Timer mGeckoReadyStartupTimer;
 
     private String mPrivateBrowsingSession;
@@ -1722,17 +1762,24 @@ public abstract class GeckoApp
 
             if (mPrivateBrowsingSession == null) {
                 sessionDataValid = parser.parse(sessionString);
             } else {
                 sessionDataValid = parser.parse(sessionString, mPrivateBrowsingSession);
             }
 
             if (tabs.length() > 0) {
+                // Update all parent tab IDs ...
+                parser.updateParentId(tabs);
                 windowObject.put("tabs", tabs);
+                // ... and for recently closed tabs as well (if we've got any).
+                JSONArray closedTabs = windowObject.optJSONArray("closedTabs");
+                parser.updateParentId(closedTabs);
+                windowObject.putOpt("closedTabs", closedTabs);
+
                 sessionString = new JSONObject().put("windows", new JSONArray().put(windowObject)).toString();
             } else {
                 if (parser.allTabsSkipped() || sessionDataValid) {
                     // If we intentionally skipped all tabs we've read from the session file, we
                     // set mShouldRestore back to false at this point already, so the calling code
                     // can infer that the exception wasn't due to a damaged session store file.
                     // The same applies if the session file was syntactically valid and
                     // simply didn't contain any tabs.