diff --git a/src/gtk/assertdlg_gtk.cpp b/src/gtk/assertdlg_gtk.cpp
index 12cc36109f..f71bba371c 100644
--- a/src/gtk/assertdlg_gtk.cpp
+++ b/src/gtk/assertdlg_gtk.cpp
@@ -177,8 +177,8 @@ static void gtk_assert_dialog_save_backtrace_callback(GtkWidget*, GtkAssertDialo
 
     dialog = gtk_file_chooser_dialog_new ("Save assert info to file", GTK_WINDOW(dlg),
                                           GTK_FILE_CHOOSER_ACTION_SAVE,
-                                          static_cast<const char*>(wxGTK_CONV(wxConvertMnemonicsToGTK(wxGetStockLabel(wxID_CANCEL)))), GTK_RESPONSE_CANCEL,
-                                          static_cast<const char*>(wxGTK_CONV(wxConvertMnemonicsToGTK(wxGetStockLabel(wxID_SAVE)))), GTK_RESPONSE_ACCEPT,
+                                          static_cast<const char*>(wxConvertMnemonicsToGTK(wxGetStockLabel(wxID_CANCEL)).utf8_str()), GTK_RESPONSE_CANCEL,
+                                          static_cast<const char*>(wxConvertMnemonicsToGTK(wxGetStockLabel(wxID_SAVE)).utf8_str()), GTK_RESPONSE_ACCEPT,
                                           NULL);
 
     if (gtk_dialog_run (GTK_DIALOG (dialog)) == GTK_RESPONSE_ACCEPT)
diff --git a/src/gtk/button.cpp b/src/gtk/button.cpp
index 6121109932..96e1fb2605 100644
--- a/src/gtk/button.cpp
+++ b/src/gtk/button.cpp
@@ -183,7 +183,7 @@ wxSize wxButtonBase::GetDefaultSize()
         GtkWidget *box = gtk_button_box_new(GTK_ORIENTATION_HORIZONTAL);
 #if defined(__WXGTK3__) && GTK_CHECK_VERSION(3,10,0)
         wxString labelGTK = GTKConvertMnemonics(wxGetStockLabel(wxID_CANCEL));
-        GtkWidget *btn = gtk_button_new_with_mnemonic(wxGTK_CONV(labelGTK));
+        GtkWidget *btn = gtk_button_new_with_mnemonic(labelGTK.utf8_str());
 #else
         GtkWidget *btn = gtk_button_new_from_stock(GTK_STOCK_CANCEL);
 #endif // GTK >= 3.10 / < 3.10