diff --git a/resources/sql/autopatches/20160720.calendar.invitetxn.php b/resources/sql/autopatches/20160720.calendar.invitetxn.php
new file mode 100644
index 0000000000..1d9ade6e67
--- /dev/null
+++ b/resources/sql/autopatches/20160720.calendar.invitetxn.php
@@ -0,0 +1,37 @@
+<?php
+
+$table = new PhabricatorCalendarEventTransaction();
+$conn_w = $table->establishConnection('w');
+
+echo pht(
+  "Restructuring calendar invite transactions...\n");
+
+foreach (new LiskMigrationIterator($table) as $txn) {
+  $type = PhabricatorCalendarEventInviteTransaction::TRANSACTIONTYPE;
+  if ($txn->getTransactionType() != $type) {
+    continue;
+  }
+
+  $old_value = array_keys($txn->getOldValue());
+
+  $orig_new = $txn->getNewValue();
+  $status_uninvited = 'uninvited';
+  foreach ($orig_new as $key => $status) {
+    if ($status == $status_uninvited) {
+      unset($orig_new[$key]);
+    }
+  }
+  $new_value = array_keys($orig_new);
+
+  queryfx(
+    $conn_w,
+    'UPDATE %T SET '.
+      'oldValue = %s, newValue = %s'.
+    'WHERE id = %d',
+    $table->getTableName(),
+    phutil_json_encode($old_value),
+    phutil_json_encode($new_value),
+    $txn->getID());
+}
+
+echo pht('Done.')."\n";
diff --git a/src/applications/calendar/xaction/PhabricatorCalendarEventInviteTransaction.php b/src/applications/calendar/xaction/PhabricatorCalendarEventInviteTransaction.php
index 69575121af..ea9355eb25 100644
--- a/src/applications/calendar/xaction/PhabricatorCalendarEventInviteTransaction.php
+++ b/src/applications/calendar/xaction/PhabricatorCalendarEventInviteTransaction.php
@@ -1,191 +1,183 @@
 <?php
 
 final class PhabricatorCalendarEventInviteTransaction
   extends PhabricatorCalendarEventTransactionType {
 
   const TRANSACTIONTYPE = 'calendar.invite';
 
   public function generateOldValue($object) {
     $status_uninvited = PhabricatorCalendarEventInvitee::STATUS_UNINVITED;
 
     $invitees = $object->getInvitees();
     foreach ($invitees as $key => $invitee) {
       if ($invitee->getStatus() == $status_uninvited) {
         unset($invitees[$key]);
       }
     }
 
-    return mpull($invitees, 'getStatus', 'getInviteePHID');
+    return array_values(mpull($invitees, 'getInviteePHID'));
   }
 
-  public function generateNewValue($object, $value) {
+  private function generateChangeMap($object, $new_value) {
     $status_invited = PhabricatorCalendarEventInvitee::STATUS_INVITED;
     $status_uninvited = PhabricatorCalendarEventInvitee::STATUS_UNINVITED;
     $status_attending = PhabricatorCalendarEventInvitee::STATUS_ATTENDING;
 
-    $invitees = $this->generateOldValue($object);
+    $old = $this->generateOldValue($object);
 
-    $new = array_fuse($value);
+    $add = array_diff($new_value, $old);
+    $rem = array_diff($old, $new_value);
 
-    $all = array_keys($invitees + $new);
     $map = array();
-    foreach ($all as $phid) {
-      $is_old = isset($invitees[$phid]);
-      $is_new = isset($new[$phid]);
-
-      if ($is_old && !$is_new) {
-        $map[$phid] = $status_uninvited;
-      } else if (!$is_old && $is_new) {
+    foreach ($add as $phid) {
         $map[$phid] = $status_invited;
-      } else {
-        $map[$phid] = $invitees[$phid];
-      }
+    }
+    foreach ($rem as $phid) {
+        $map[$phid] = $status_uninvited;
     }
 
     // If we're creating this event and the actor is inviting themselves,
     // mark them as attending.
     if ($this->isNewObject()) {
       $acting_phid = $this->getActingAsPHID();
       if (isset($map[$acting_phid])) {
         $map[$acting_phid] = $status_attending;
       }
     }
 
     return $map;
   }
 
   public function applyExternalEffects($object, $value) {
-    $phids = array_keys($value);
+    $map = $this->generateChangeMap($object, $value);
+
     $invitees = $object->getInvitees();
     $invitees = mpull($invitees, null, 'getInviteePHID');
 
-    foreach ($phids as $phid) {
+    foreach ($map as $phid => $status) {
       $invitee = idx($invitees, $phid);
       if (!$invitee) {
         $invitee = id(new PhabricatorCalendarEventInvitee())
           ->setEventPHID($object->getPHID())
           ->setInviteePHID($phid)
           ->setInviterPHID($this->getActingAsPHID());
         $invitees[] = $invitee;
       }
-      $invitee->setStatus($value[$phid])
+      $invitee->setStatus($status)
         ->save();
     }
 
     $object->attachInvitees($invitees);
   }
 
   public function validateTransactions($object, array $xactions) {
     $actor = $this->getActor();
 
     $errors = array();
 
     $old = $object->getInvitees();
     $old = mpull($old, null, 'getInviteePHID');
     foreach ($xactions as $xaction) {
       $new = $xaction->getNewValue();
       $new = array_fuse($new);
       $add = array_diff_key($new, $old);
       if (!$add) {
         continue;
       }
 
       // In the UI, we only allow you to invite mailable objects, but there
       // is no definitive marker for "invitable object" today. Just allow
       // any valid object to be invited.
       $objects = id(new PhabricatorObjectQuery())
         ->setViewer($actor)
         ->withPHIDs($add)
         ->execute();
       $objects = mpull($objects, null, 'getPHID');
       foreach ($add as $phid) {
         if (isset($objects[$phid])) {
           continue;
         }
 
         $errors[] = $this->newInvalidError(
           pht(
             'Invitee "%s" identifies an object that does not exist or '.
             'which you do not have permission to view.',
             $phid),
           $xaction);
       }
     }
 
     return $errors;
   }
 
   public function getIcon() {
     return 'fa-user-plus';
   }
 
   public function getTitle() {
     list($add, $rem) = $this->getChanges();
 
     if ($add && !$rem) {
       return pht(
         '%s invited %s attendee(s): %s.',
         $this->renderAuthor(),
         phutil_count($add),
         $this->renderHandleList($add));
     } else if (!$add && $rem) {
       return pht(
         '%s uninvited %s attendee(s): %s.',
         $this->renderAuthor(),
         phutil_count($rem),
         $this->renderHandleList($rem));
     } else {
       return pht(
         '%s invited %s attendee(s): %s; uninvinted %s attendee(s): %s.',
         $this->renderAuthor(),
         phutil_count($add),
         $this->renderHandleList($add),
         phutil_count($rem),
         $this->renderHandleList($rem));
     }
   }
 
   public function getTitleForFeed() {
     list($add, $rem) = $this->getChanges();
 
     if ($add && !$rem) {
       return pht(
         '%s invited %s attendee(s) to %s: %s.',
         $this->renderAuthor(),
         phutil_count($add),
         $this->renderObject(),
         $this->renderHandleList($add));
     } else if (!$add && $rem) {
       return pht(
         '%s uninvited %s attendee(s) to %s: %s.',
         $this->renderAuthor(),
         phutil_count($rem),
         $this->renderObject(),
         $this->renderHandleList($rem));
     } else {
       return pht(
         '%s updated the invite list for %s, invited %s: %s; '.
         'uninvinted %s: %s.',
         $this->renderAuthor(),
         $this->renderObject(),
         phutil_count($add),
         $this->renderHandleList($add),
         phutil_count($rem),
         $this->renderHandleList($rem));
     }
   }
 
   private function getChanges() {
     $old = $this->getOldValue();
     $new = $this->getNewValue();
 
-    $add = array_diff_key($new, $old);
-    $rem = array_diff_key($old, $new);
-
-    $add = array_keys($add);
-    $rem = array_keys($rem);
+    $add = array_diff($new, $old);
+    $rem = array_diff($old, $new);
 
     return array(array_fuse($add), array_fuse($rem));
   }
 
 }