diff --git a/src/core/slaveinterface.cpp b/src/core/slaveinterface.cpp
index 6eb2b08d..d79b498d 100644
--- a/src/core/slaveinterface.cpp
+++ b/src/core/slaveinterface.cpp
@@ -103,7 +103,9 @@ void SlaveInterface::calcSpeed()
     // using first and last item from the list.
 
     const qint64 elapsed_time = d->elapsed_timer.elapsed();
-    if (elapsed_time >= 900) {
+    const qint64 last_time = d->transfer_details.isEmpty() ? 0 : d->transfer_details.last().time;
+
+    if (elapsed_time - last_time >= 900) {
         if (d->transfer_details.count() == max_count) {
             d->transfer_details.removeFirst();
         }