diff --git a/src/calibre/devices/kobo/driver.py b/src/calibre/devices/kobo/driver.py
index 7a37cb19c9..d367cc251d 100644
--- a/src/calibre/devices/kobo/driver.py
+++ b/src/calibre/devices/kobo/driver.py
@@ -85,7 +85,7 @@ class KOBO(USBMS):
 
                 idx = bl_cache.get(lpath, None)
                 if idx is not None:
-                    imagename = self.normalize_path(prefix + '.kobo/images/' + ImageID + ' - NickelBookCover.parsed')
+                    imagename = self.normalize_path(self._main_prefix + '.kobo/images/' + ImageID + ' - NickelBookCover.parsed')
                     #print "Image name Normalized: " + imagename
                     bl[idx].thumbnail = ImageWrapper(imagename)
                     bl_cache[lpath] = None