--- a/QTfrontend/ui/page/pagetraining.cpp	Wed Dec 19 01:02:06 2018 +0100
+++ b/QTfrontend/ui/page/pagetraining.cpp	Wed Dec 19 01:21:20 2018 +0100
@@ -321,6 +321,8 @@
 
             if (QFile::exists(thumbFile))
                 btnPreview->setIcon(QIcon(thumbFile));
+            else if (tbw->currentWidget() == lstChallenges)
+                btnPreview->setIcon(QIcon(":/res/Challenges.png"));
             else
                 btnPreview->setIcon(QIcon(":/res/Trainings.png"));