diff --git a/astrid/plugin-src/com/todoroo/astrid/actfm/ActFmPreferences.java b/astrid/plugin-src/com/todoroo/astrid/actfm/ActFmPreferences.java
index 3980ae393..1e5fb59a3 100644
--- a/astrid/plugin-src/com/todoroo/astrid/actfm/ActFmPreferences.java
+++ b/astrid/plugin-src/com/todoroo/astrid/actfm/ActFmPreferences.java
@@ -1,5 +1,6 @@
 package com.todoroo.astrid.actfm;
 
+import android.content.DialogInterface;
 import android.content.Intent;
 import android.content.res.Resources;
 import android.preference.Preference;
@@ -7,8 +8,10 @@ import android.preference.PreferenceCategory;
 
 import com.timsu.astrid.R;
 import com.todoroo.andlib.service.Autowired;
+import com.todoroo.andlib.utility.DialogUtilities;
 import com.todoroo.astrid.actfm.sync.ActFmPreferenceService;
 import com.todoroo.astrid.actfm.sync.ActFmSyncV2Provider;
+import com.todoroo.astrid.gtasks.GtasksPreferenceService;
 import com.todoroo.astrid.sync.SyncProviderPreferences;
 import com.todoroo.astrid.sync.SyncProviderUtilities;
 
@@ -22,6 +25,7 @@ import com.todoroo.astrid.sync.SyncProviderUtilities;
 public class ActFmPreferences extends SyncProviderPreferences {
 
     @Autowired ActFmPreferenceService actFmPreferenceService;
+    @Autowired GtasksPreferenceService gtasksPreferenceService;
 
     @Override
     public int getPreferenceResource() {
@@ -31,14 +35,28 @@ public class ActFmPreferences extends SyncProviderPreferences {
     @Override
     public void startSync() {
         if (!actFmPreferenceService.isLoggedIn()) {
-            Intent intent = new Intent(this, ActFmLoginActivity.class);
-            startActivityForResult(intent, REQUEST_LOGIN);
+            if (gtasksPreferenceService.isLoggedIn()) {
+                DialogUtilities.okCancelDialog(this, getString(R.string.DLG_warning), getString(R.string.actfm_dual_sync_warning),
+                        new DialogInterface.OnClickListener() {
+                            @Override
+                            public void onClick(DialogInterface dialog, int which) {
+                                startLogin();
+                            }
+                        }, null);
+            } else {
+                startLogin();
+            }
         } else {
             setResult(RESULT_CODE_SYNCHRONIZE);
             finish();
         }
     }
 
+    private void startLogin() {
+        Intent intent = new Intent(this, ActFmLoginActivity.class);
+        startActivityForResult(intent, REQUEST_LOGIN);
+    }
+
     @Override
     public void logOut() {
         new ActFmSyncV2Provider().signOut();
diff --git a/astrid/plugin-src/com/todoroo/astrid/gtasks/GtasksPreferences.java b/astrid/plugin-src/com/todoroo/astrid/gtasks/GtasksPreferences.java
index 48ea5f42e..6209bfaa9 100644
--- a/astrid/plugin-src/com/todoroo/astrid/gtasks/GtasksPreferences.java
+++ b/astrid/plugin-src/com/todoroo/astrid/gtasks/GtasksPreferences.java
@@ -1,11 +1,14 @@
 package com.todoroo.astrid.gtasks;
 
+import android.content.DialogInterface;
 import android.content.Intent;
 import android.os.Bundle;
 
 import com.timsu.astrid.R;
 import com.todoroo.andlib.service.Autowired;
 import com.todoroo.andlib.service.DependencyInjectionService;
+import com.todoroo.andlib.utility.DialogUtilities;
+import com.todoroo.astrid.actfm.sync.ActFmPreferenceService;
 import com.todoroo.astrid.gtasks.auth.GtasksLoginActivity;
 import com.todoroo.astrid.gtasks.sync.GtasksSyncV2Provider;
 import com.todoroo.astrid.sync.SyncProviderPreferences;
@@ -21,6 +24,7 @@ import com.todoroo.astrid.sync.SyncProviderUtilities;
 public class GtasksPreferences extends SyncProviderPreferences {
 
     @Autowired private GtasksPreferenceService gtasksPreferenceService;
+    @Autowired private ActFmPreferenceService actFmPreferenceService;
 
     public GtasksPreferences() {
         super();
@@ -40,14 +44,28 @@ public class GtasksPreferences extends SyncProviderPreferences {
     @Override
     public void startSync() {
         if (!gtasksPreferenceService.isLoggedIn()) {
-            Intent intent = new Intent(this, GtasksLoginActivity.class);
-            startActivityForResult(intent, REQUEST_LOGIN);
+            if (actFmPreferenceService.isLoggedIn()) {
+                DialogUtilities.okCancelDialog(this, getString(R.string.DLG_warning), getString(R.string.gtasks_dual_sync_warning),
+                        new DialogInterface.OnClickListener() {
+                            @Override
+                            public void onClick(DialogInterface dialog, int which) {
+                                startLogin();
+                            }
+                        }, null);
+            } else {
+                startLogin();
+            }
         } else {
             setResult(RESULT_CODE_SYNCHRONIZE);
             finish();
         }
     }
 
+    private void startLogin() {
+        Intent intent = new Intent(this, GtasksLoginActivity.class);
+        startActivityForResult(intent, REQUEST_LOGIN);
+    }
+
     @Override
     public void logOut() {
         GtasksSyncV2Provider.getInstance().signOut();
diff --git a/astrid/res/values/strings-actfm.xml b/astrid/res/values/strings-actfm.xml
index 43415617a..7fc6d3fb0 100644
--- a/astrid/res/values/strings-actfm.xml
+++ b/astrid/res/values/strings-actfm.xml
@@ -287,5 +287,9 @@
   <!-- text for notification when comments are received -->
   <string name="actfm_notification_comments">New comments received / click for more details</string>
     
+  <string name="actfm_dual_sync_warning">You are currently synchronizing with Google Tasks. 
+      Be advised that synchronizing with both services can in some cases lead to unexpected results. 
+      Are you sure you want to sync with Astrid.com?</string>
+  
 </resources>
 
diff --git a/astrid/res/values/strings-core.xml b/astrid/res/values/strings-core.xml
index 4c806f404..5742df960 100644
--- a/astrid/res/values/strings-core.xml
+++ b/astrid/res/values/strings-core.xml
@@ -67,6 +67,8 @@
   
   <string name="DLG_undo">Undo</string>
   
+  <string name="DLG_warning">Warning</string>
+  
   <!-- =============================================================== UI == -->
   
   <!-- Label for DateButtons with no value -->
diff --git a/astrid/res/values/strings-gtasks.xml b/astrid/res/values/strings-gtasks.xml
index 9c3c3f65d..e9754ebb3 100644
--- a/astrid/res/values/strings-gtasks.xml
+++ b/astrid/res/values/strings-gtasks.xml
@@ -104,6 +104,9 @@
     <!-- Error when authorization error happens in background sync -->
     <string name="gtasks_error_background_sync_auth">Error authenticating in background. Please try initiating a sync while Astrid is running.</string>
     
+    <string name="gtasks_dual_sync_warning">You are currently synchronizing with Astrid.com. 
+      Be advised that synchronizing with both services can in some cases lead to unexpected results. 
+      Are you sure you want to sync with Google Tasks?</string>
         
 </resources>