diff --git a/libsolutil/JSON.h b/libsolutil/JSON.h
index 1f2fa2171..572cc43c4 100644
--- a/libsolutil/JSON.h
+++ b/libsolutil/JSON.h
@@ -23,6 +23,7 @@
 
 #pragma once
 
+#define JSON_DIAGNOSTICS 1
 #include <libsolutil/nlohmannjson.hpp>
 
 #include <string>