diff --git a/src/aphront/response/AphrontFileResponse.php b/src/aphront/response/AphrontFileResponse.php
--- a/src/aphront/response/AphrontFileResponse.php
+++ b/src/aphront/response/AphrontFileResponse.php
@@ -8,7 +8,14 @@
   private $compressResponse;
 
   private $mimeType;
+
+  /**
+   * Download filename
+   *
+   * This is NULL as default or a string.
+   */
   private $download;
+
   private $rangeMin;
   private $rangeMax;
   private $allowOrigins = array();
@@ -18,14 +25,31 @@
     return $this;
   }
 
+  /**
+   * Activate a download, and set the download filename
+   *
+   * @param $download mixed
+   * @return self
+   */
   public function setDownload($download) {
-    if (!phutil_nonempty_string($download)) {
-      $download = 'untitled';
+
+    // Try converting any scalar to string
+    $download = (string)$download;
+
+    // Assume a nice default
+    if ($download === '') {
+        $download = 'untitled';
     }
+
     $this->download = $download;
     return $this;
   }
 
+  /**
+   * Get the download filename
+   *
+   * @return mixed
+   */
   public function getDownload() {
     return $this->download;
   }
@@ -113,7 +137,7 @@
       $headers[] = array('Content-Length', $content_len);
     }
 
-    if (strlen($this->getDownload())) {
+    if (phutil_nonempty_string($this->getDownload())) {
       $headers[] = array('X-Download-Options', 'noopen');
 
       $filename = $this->getDownload();