diff --git a/src/calibre/gui2/__init__.py b/src/calibre/gui2/__init__.py
index 6a3c48e6e9..1e028d48b0 100644
--- a/src/calibre/gui2/__init__.py
+++ b/src/calibre/gui2/__init__.py
@@ -1153,7 +1153,10 @@ class Application(QApplication):
             transient_scroller = transient_scroller()
         icon_map[(QStyle.StandardPixmap.SP_CustomBase & 0xf0000000) + 1] = I('close-for-light-theme.png')
         icon_map[(QStyle.StandardPixmap.SP_CustomBase & 0xf0000000) + 2] = I('close-for-dark-theme.png')
-        self.pi.load_style(icon_map, transient_scroller)
+        try:
+            self.pi.load_style(icon_map, transient_scroller)
+        except OverflowError:  # running from source without updated runtime
+            self.pi.load_style({}, transient_scroller)
 
     def _send_file_open_events(self):
         with self._file_open_lock: