diff --git a/src/slic3r/GUI/MainFrame.cpp b/src/slic3r/GUI/MainFrame.cpp
index 3b902879c..9c7533acd 100644
--- a/src/slic3r/GUI/MainFrame.cpp
+++ b/src/slic3r/GUI/MainFrame.cpp
@@ -658,7 +658,7 @@ void MainFrame::init_tabpanel()
 #endif
 #if ENABLE_VALIDATE_CUSTOM_GCODE
         if (int old_selection = e.GetOldSelection();
-            old_selection != wxNOT_FOUND && old_selection < m_tabpanel->GetPageCount()) {
+            old_selection != wxNOT_FOUND && old_selection < static_cast<int>(m_tabpanel->GetPageCount())) {
             Tab* old_tab = dynamic_cast<Tab*>(m_tabpanel->GetPage(old_selection));
             if (old_tab)
                 old_tab->validate_custom_gcodes();