diff --git a/src/applications/auth/engine/PhabricatorAuthPasswordEngine.php b/src/applications/auth/engine/PhabricatorAuthPasswordEngine.php
--- a/src/applications/auth/engine/PhabricatorAuthPasswordEngine.php
+++ b/src/applications/auth/engine/PhabricatorAuthPasswordEngine.php
@@ -156,8 +156,10 @@
     $terms_map = array();
     foreach ($blocklist as $term) {
       $terms_map[$term] = $term;
-      foreach (preg_split('/[ @.]/', $term) as $subterm) {
-        $terms_map[$subterm] = $term;
+      if (phutil_nonempty_string($term)) {
+        foreach (preg_split('/[ @.]/', $term) as $subterm) {
+          $terms_map[$subterm] = $term;
+        }
       }
     }