diff --git a/lib/response.js b/lib/response.js
index c1514901c5..a4f10cbb2e 100644
--- a/lib/response.js
+++ b/lib/response.js
@@ -1135,6 +1135,7 @@ function stringify (value, replacer, spaces, escape) {
           return '\\u003e'
         case 0x26:
           return '\\u0026'
+        /* istanbul ignore next: unreachable default */
         default:
           return c
       }