diff --git a/src/util/json/Writer.cpp b/src/util/json/Writer.cpp
index de58649..e369897 100644
--- a/src/util/json/Writer.cpp
+++ b/src/util/json/Writer.cpp
@@ -111,7 +111,7 @@ void Writer::val(const Val& v) {
       val(Null());
       return;
     case Val::UINT:
-      val(v.ui);
+      val((int)v.ui);
       return;
     case Val::INT:
       val(v.i);