diff --git a/app/assets/dash_v1.js b/app/assets/dash_v1.js
index 665d8e3..37b39f0 100644
--- a/app/assets/dash_v1.js
+++ b/app/assets/dash_v1.js
@@ -5,7 +5,7 @@ function output(inp) {
 function syntaxHighlight(json) {
     console.log(json)
     json = JSON.stringify(JSON.parse(json.replace(/"/g, '"')), undefined, 4)
-    json = json.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
+    json = json.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/\p{C}+/g, '?'); // replace all non-printable characters
     return json.replace(/("(\\u[a-zA-Z0-9]{4}|\\[^u]|[^\\"])*"(\s*:)?|\b(true|false|null)\b|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?)/g, function (match) {
         var cls = 'number';
         if (/^"/.test(match)) {
@@ -25,6 +25,6 @@ function syntaxHighlight(json) {
 
 function from_server(json_string){
     console.log(json_string)
-    json_string = JSON.parse(json_string.replace(/&quot;/g, '"'))
+    json_string = JSON.parse(json_string.replace(/&quot;/g, '"').replace(/\p{C}+/g, '?'))
     window.devbug = json_string
 }