diff --git a/worker.h b/worker.h
index 80ff5c1..d1f2d9c 100644
--- a/worker.h
+++ b/worker.h
@@ -226,7 +226,7 @@ class Worker : public QThread{
                 if (m_worker->smap.contains(last)) {
                     lst << QString(" (last failed step: %1)").arg(m_worker->smap[last]);
                 } else {
-                    lst << QString(" (last failed step unknown: %1)").arg(last);
+                    lst << QString(" (last failed step unknown: %1)").arg((int)(last));
                 }
                 m_worker->GUI(lst) << (m_worker->CONSOLE(lst) << (m_worker->ISMAS(lst) << UPDATE_STEP::UPDATE_FAILED));
             }