diff --git a/src/utils/utils.php b/src/utils/utils.php
--- a/src/utils/utils.php
+++ b/src/utils/utils.php
@@ -1888,7 +1888,10 @@
  * @return  string  URI encoded string, except for '/'.
  */
 function phutil_escape_uri($string) {
-  return str_replace('%2F', '/', rawurlencode($string));
+  if (phutil_nonempty_string($string)) {
+    return str_replace('%2F', '/', rawurlencode($string));
+  }
+  return null;
 }