diff --git a/src/Task.cpp b/src/Task.cpp
index b1339f8b7..01677310f 100644
--- a/src/Task.cpp
+++ b/src/Task.cpp
@@ -1962,7 +1962,7 @@ void Task::modify (modType type, bool text_required /* = false */)
             // If v is duration, add 'now' to it, else store as date.
             if (v.type () == Variant::type_duration)
             {
-              context.debug (label + name + " <-- '" + format ("{1}", std::to_string (v.get_duration ())) + "' <-- '" + (std::string) v + "' <-- '" + value + "'");
+              context.debug (label + name + " <-- '" + format ("{1}", format (v.get_duration ())) + "' <-- '" + (std::string) v + "' <-- '" + value + "'");
               Variant now;
               if (namedDates ("now", now))
                 v += now;