diff --git a/src/aphront/AphrontRequest.php b/src/aphront/AphrontRequest.php
--- a/src/aphront/AphrontRequest.php
+++ b/src/aphront/AphrontRequest.php
@@ -448,7 +448,7 @@
   }
 
   private function getPrefixedCookieName($name) {
-    if (strlen($this->cookiePrefix)) {
+    if (phutil_nonempty_string($this->cookiePrefix)) {
       return $this->cookiePrefix.'_'.$name;
     } else {
       return $name;