diff --git a/src/future/http/status/HTTPFutureHTTPResponseStatus.php b/src/future/http/status/HTTPFutureHTTPResponseStatus.php
index 44636dca..a63130fd 100644
--- a/src/future/http/status/HTTPFutureHTTPResponseStatus.php
+++ b/src/future/http/status/HTTPFutureHTTPResponseStatus.php
@@ -11,6 +11,8 @@ final class HTTPFutureHTTPResponseStatus extends HTTPFutureResponseStatus {
     array $headers,
     $expect = null) {
 
+    // As $body can be null (T15930), make sure this code deals with a string
+    $body = phutil_string_cast($body);
     // NOTE: Avoiding PhutilUTF8StringTruncator here because this isn't lazy
     // and responses may be large.
     if (strlen($body) > 512) {