--- a/mobile/android/base/BrowserApp.java
+++ b/mobile/android/base/BrowserApp.java
@@ -515,21 +515,22 @@ public class BrowserApp extends GeckoApp
         }).execute();
     }
 
     @Override
     public void onCreate(Bundle savedInstanceState) {
         mAboutHomeStartupTimer = new Telemetry.UptimeTimer("FENNEC_STARTUP_TIME_ABOUTHOME");
 
         final Intent intent = getIntent();
-        final String args = intent.getStringExtra("args");
-
-        if (GuestSession.shouldUse(this, args)) {
-            mProfile = GeckoProfile.createGuestProfile(this);
-        } else {
+        final GeckoProfile p = GeckoProfile.get(this);
+        if (p != null && !p.inGuestMode()) {
+            // This is *only* valid because we never want to use the guest mode
+            // profile concurrently with a normal profile -- no syncing to it,
+            // no dual-profile usage, nothing. BrowserApp startup with a conventional
+            // GeckoProfile will cause the guest profile to be deleted.
             GeckoProfile.maybeCleanupGuestProfile(this);
         }
 
         // This has to be prepared prior to calling GeckoApp.onCreate, because
         // widget code and BrowserToolbar need it, and they're created by the
         // layout, which GeckoApp takes care of.
         ((GeckoApplication) getApplication()).prepareLightweightTheme();
         super.onCreate(savedInstanceState);

--- a/mobile/android/base/GeckoProfile.java
+++ b/mobile/android/base/GeckoProfile.java
@@ -18,16 +18,17 @@ import java.util.Hashtable;
 import org.mozilla.gecko.GeckoProfileDirectories.NoMozillaDirectoryException;
 import org.mozilla.gecko.GeckoProfileDirectories.NoSuchProfileException;
 import org.mozilla.gecko.db.LocalBrowserDB;
 import org.mozilla.gecko.distribution.Distribution;
 import org.mozilla.gecko.mozglue.RobocopTarget;
 import org.mozilla.gecko.util.INIParser;
 import org.mozilla.gecko.util.INISection;
 
+import android.app.Activity;
 import android.content.ContentResolver;
 import android.content.Context;
 import android.content.Intent;
 import android.support.v4.content.LocalBroadcastManager;
 import android.text.TextUtils;
 import android.util.Log;
 
 public final class GeckoProfile {
@@ -85,19 +86,29 @@ public final class GeckoProfile {
             // Check for a cached profile on this context already
             // TODO: We should not be caching profile information on the Activity context
             final GeckoApp geckoApp = (GeckoApp) context;
             if (geckoApp.mProfile != null) {
                 return geckoApp.mProfile;
             }
         }
 
-        // If the guest profile should be used return it.
-        if (GuestSession.shouldUse(context, "")) {
-            return GeckoProfile.getGuestProfile(context);
+        final String args;
+        if (context instanceof Activity) {
+            args = ((Activity) context).getIntent().getStringExtra("args");
+        } else {
+            args = null;
+        }
+
+        if (GuestSession.shouldUse(context, args)) {
+            GeckoProfile p = GeckoProfile.getOrCreateGuestProfile(context);
+            if (isGeckoApp) {
+                ((GeckoApp) context).mProfile = p;
+            }
+            return p;
         }
 
         if (isGeckoApp) {
             final GeckoApp geckoApp = (GeckoApp) context;
             String defaultProfileName;
             try {
                 defaultProfileName = geckoApp.getDefaultProfileName();
             } catch (NoMozillaDirectoryException e) {
@@ -186,16 +197,17 @@ public final class GeckoProfile {
             // Clear all shared prefs for the given profile.
             GeckoSharedPrefs.forProfileName(context, profileName)
                             .edit().clear().apply();
         }
 
         return success;
     }
 
+    // Only public for access from tests.
     public static GeckoProfile createGuestProfile(Context context) {
         try {
             // We need to force the creation of a new guest profile if we want it outside of the normal profile path,
             // otherwise GeckoProfile.getDir will try to be smart and build it for us in the normal profiles dir.
             getGuestDir(context).mkdir();
             GeckoProfile profile = getGuestProfile(context);
 
             // If we're creating this guest session over the keyguard, don't lock it.
@@ -227,16 +239,28 @@ public final class GeckoProfile {
 
     private static File getGuestDir(Context context) {
         if (sGuestDir == null) {
             sGuestDir = context.getFileStreamPath("guest");
         }
         return sGuestDir;
     }
 
+    /**
+     * Performs IO. Be careful of using this on the main thread.
+     */
+    public static GeckoProfile getOrCreateGuestProfile(Context context) {
+        GeckoProfile p = getGuestProfile(context);
+        if (p == null) {
+            return createGuestProfile(context);
+        }
+
+        return p;
+    }
+
     public static GeckoProfile getGuestProfile(Context context) {
         if (sGuestProfile == null) {
             File guestDir = getGuestDir(context);
             if (guestDir.exists()) {
                 sGuestProfile = get(context, GUEST_PROFILE, guestDir);
                 sGuestProfile.mInGuestMode = true;
             }
         }