diff --git a/lib_convert/src/main/x/convert/formats/JsonFormat.x b/lib_convert/src/main/x/convert/formats/JsonFormat.x
index c2ea6b6b0..42979f490 100644
--- a/lib_convert/src/main/x/convert/formats/JsonFormat.x
+++ b/lib_convert/src/main/x/convert/formats/JsonFormat.x
@@ -28,8 +28,8 @@ const JsonFormat(Printer printer = Printer.DEFAULT)
 
     @Override
     Value decode(String text) {
-        if (Doc doc := new Parser(new CharArrayReader(text)).next()) {
-            return doc;
+        if (Doc doc := new Parser(text.toReader()).next()) {
+            return doc.makeImmutable();
         } else {
             return Null;
         }