diff --git a/resources/sql/autopatches/20141107.phriction.popkeys.php b/resources/sql/autopatches/20141107.phriction.popkeys.php
new file mode 100644
index 0000000000..9af7e3a952
--- /dev/null
+++ b/resources/sql/autopatches/20141107.phriction.popkeys.php
@@ -0,0 +1,29 @@
+<?php
+
+$table = new PhrictionDocument();
+$conn_w = $table->establishConnection('w');
+
+echo "Populating Phriction mailkeys.\n";
+
+foreach (new LiskMigrationIterator($table) as $doc) {
+  $id = $doc->getID();
+
+  $key = $doc->getMailKey();
+  if ((strlen($key) == 20) && (strpos($key, "\0") === false)) {
+    // To be valid, keys must have length 20 and not contain any null bytes.
+    // See T6487.
+    echo "Document has valid mailkey.\n";
+    continue;
+  } else {
+    echo "Populating mailkey for document {$id}...\n";
+    $mail_key = Filesystem::readRandomCharacters(20);
+    queryfx(
+      $conn_w,
+      'UPDATE %T SET mailKey = %s WHERE id = %d',
+      $table->getTableName(),
+      $mail_key,
+      $id);
+  }
+}
+
+echo "Done.\n";