diff --git a/lib/tools.js b/lib/tools.js
index 92bd23ba6..3bb74ee04 100644
--- a/lib/tools.js
+++ b/lib/tools.js
@@ -73,6 +73,9 @@ function genLog (level, hook) {
   }
 }
 
+// eslint-disable-next-line
+const STR_ESCAPE = /[\u0000-\u001f\u0022\u005c\ud800-\udfff]|[\ud800-\udbff](?![\udc00-\udfff])|(?:[^\ud800-\udbff]|^)[\udc00-\udfff]/
+
 // magically escape strings for json
 // relying on their charCodeAt
 // everything below 32 needs JSON.stringify()
@@ -84,6 +87,9 @@ function asString (str) {
   let found = false
   let point = 255
   const l = str.length
+  if (!STR_ESCAPE.test(str)) {
+    return '"' + str + '"'
+  }
   if (l > 100) {
     return JSON.stringify(str)
   }