diff --git a/src/variant.cpp b/src/variant.cpp
index 9df67da..e1d6df7 100644
--- a/src/variant.cpp
+++ b/src/variant.cpp
@@ -693,7 +693,7 @@ string      format_string( const string& format, const variant_object& args )
            {
               if( val->value().is_object() || val->value().is_array() )
               {
-                ss << json::to_string( val->value() );
+                ss << '\n' << json::to_pretty_string( val->value() );
               } 
               else 
               {