diff --git a/actions/apifriendshipscreate.php b/actions/apifriendshipscreate.php
index e7caf96869..3997a8b51c 100644
--- a/actions/apifriendshipscreate.php
+++ b/actions/apifriendshipscreate.php
@@ -100,8 +100,8 @@ class ApiFriendshipsCreateAction extends ApiAuthAction
 
         try {
             Subscription::start($this->scoped, $this->other);
-        } catch (Exception $e) {
-            $this->clientError($e->getMessage(), 403);
+        } catch (AlreadyFulfilledException $e) {
+            $this->clientError($e->getMessage(), 409);
         }
 
         $this->initDocument($this->format);
diff --git a/actions/atompubsubscriptionfeed.php b/actions/atompubsubscriptionfeed.php
index 413277a5d3..6a483b95c0 100644
--- a/actions/atompubsubscriptionfeed.php
+++ b/actions/atompubsubscriptionfeed.php
@@ -230,18 +230,11 @@ class AtompubsubscriptionfeedAction extends AtompubAction
                 $this->clientError(sprintf(_('Unknown profile %s.'), $person->id));
             }
 
-            if (Subscription::exists($this->_profile, $profile)) {
+            try {
+                $sub = Subscription::start($this->_profile, $profile);
+            } catch (AlreadyFulfilledException $e) {
                 // 409 Conflict
-                // TRANS: Client error displayed trying to subscribe to an already subscribed profile.
-                // TRANS: %s is the profile the user already has a subscription on.
-                $this->clientError(sprintf(_('Already subscribed to %s.'),
-                                           $person->id),
-                                   409);
-            }
-
-            if (Subscription::start($this->_profile, $profile)) {
-                $sub = Subscription::pkeyGet(array('subscriber' => $this->_profile->id,
-                                                   'subscribed' => $profile->id));
+                $this->clientError($e->getMessage(), 409);
             }
 
             Event::handle('EndAtomPubNewActivity', array($activity, $sub));
diff --git a/actions/invite.php b/actions/invite.php
index f99dd4d783..89b7e83bf6 100644
--- a/actions/invite.php
+++ b/actions/invite.php
@@ -118,7 +118,7 @@ class InviteAction extends Action
                         $this->already[] = $other;
                     } else {
                         try {
-                            Subscription::start($profile, $other);
+                            Subscription::ensureStart($profile, $other);
                             $this->subbed[] = $other;
                         } catch (Exception $e) {
                             // subscription failed, but keep working
diff --git a/actions/subscribe.php b/actions/subscribe.php
index 4002c9fbb0..320409afa0 100644
--- a/actions/subscribe.php
+++ b/actions/subscribe.php
@@ -122,7 +122,7 @@ class SubscribeAction extends Action
     {
         // Throws exception on error
 
-        $sub = Subscription::start($this->user->getProfile(),
+        $sub = Subscription::ensureStart($this->user->getProfile(),
                                    $this->other);
 
         if ($this->boolean('ajax')) {
diff --git a/classes/Subscription.php b/classes/Subscription.php
index 5c5101ad1d..ec9ae51841 100644
--- a/classes/Subscription.php
+++ b/classes/Subscription.php
@@ -94,6 +94,7 @@ class Subscription extends Managed_DataObject
         if (Event::handle('StartSubscribe', array($subscriber, $other))) {
             $otherUser = User::getKV('id', $other->id);
             if ($otherUser instanceof User && $otherUser->subscribe_policy == User::SUBSCRIBE_POLICY_MODERATE && !$force) {
+                // Will throw an AlreadyFulfilledException if this queue item already exists.
                 $sub = Subscription_queue::saveNew($subscriber, $other);
                 $sub->notify();
             } else {
@@ -132,6 +133,17 @@ class Subscription extends Managed_DataObject
         return $sub;
     }
 
+    static function ensureStart(Profile $subscriber, Profile $other, $force=false)
+    {
+        try {
+            $sub = self::start($subscriber, $other, $force);
+        } catch (AlreadyFulfilledException $e) {
+            // Nothing to see here, move along...
+            return self::getSubscription($subscriber, $other);
+        }
+        return $sub;
+    }
+
     /**
      * Low-level subscription save.
      * Outside callers should use Subscription::start()
diff --git a/classes/Subscription_queue.php b/classes/Subscription_queue.php
index 405eca93fd..02cc72f1f2 100644
--- a/classes/Subscription_queue.php
+++ b/classes/Subscription_queue.php
@@ -36,6 +36,9 @@ class Subscription_queue extends Managed_DataObject
 
     public static function saveNew(Profile $subscriber, Profile $subscribed)
     {
+        if (self::exists($subscriber, $subscribed)) {
+            throw new AlreadyFulfilledException(_('This subscription request is already in progress.'));
+        }
         $rq = new Subscription_queue();
         $rq->subscriber = $subscriber->id;
         $rq->subscribed = $subscribed->id;
diff --git a/classes/User.php b/classes/User.php
index 2f4670a2df..f543a75528 100644
--- a/classes/User.php
+++ b/classes/User.php
@@ -354,7 +354,7 @@ class User extends Managed_DataObject
                     common_log(LOG_WARNING, sprintf("Default user %s does not exist.", $defnick),
                                __FILE__);
                 } else {
-                    Subscription::start($profile, $defuser->getProfile());
+                    Subscription::ensureStart($profile, $defuser->getProfile());
                 }
             }
 
diff --git a/lib/activityimporter.php b/lib/activityimporter.php
index 5bef4cfb07..c4dd797e6d 100644
--- a/lib/activityimporter.php
+++ b/lib/activityimporter.php
@@ -109,7 +109,7 @@ class ActivityImporter extends QueueHandler
 
             // XXX: don't do this for untrusted input!
 
-            Subscription::start($otherProfile, $profile);
+            Subscription::ensureStart($otherProfile, $profile);
         } else if (empty($activity->actor)
                    || $activity->actor->id == $author->id) {
 
@@ -123,7 +123,7 @@ class ActivityImporter extends QueueHandler
                 throw new ClientException(_('Unknown profile.'));
             }
 
-            Subscription::start($profile, $otherProfile);
+            Subscription::ensureStart($profile, $otherProfile);
         } else {
             // TRANS: Client exception thrown when trying to import an event not related to the importing user.
             throw new Exception(_('This activity seems unrelated to our user.'));
diff --git a/lib/activitymover.php b/lib/activitymover.php
index fe33e9081e..ac828d9491 100644
--- a/lib/activitymover.php
+++ b/lib/activitymover.php
@@ -146,7 +146,7 @@ class ActivityMover extends QueueHandler
                                "Changing sub to {$act->objects[0]->id}".
                                "by {$act->actor->id} to {$remote->nickname}.");
                     $otherProfile = $otherUser->getProfile();
-                    Subscription::start($otherProfile, $remote);
+                    Subscription::ensureStart($otherProfile, $remote);
                     Subscription::cancel($otherProfile, $user->getProfile());
                 } else {
                     $this->log(LOG_NOTICE,