diff --git a/src/calibre/devices/prs505/driver.py b/src/calibre/devices/prs505/driver.py
index 165dd324ad..6c7049d8e8 100644
--- a/src/calibre/devices/prs505/driver.py
+++ b/src/calibre/devices/prs505/driver.py
@@ -183,6 +183,9 @@ class PRS505(CLI, Device):
         return zip(paths, sizes, ctimes, cycle([on_card]))
 
     def add_books_to_metadata(self, locations, metadata, booklists):
+        if not locations or not metadata:
+            return
+        
         metadata = iter(metadata)
         for location in locations:
             info = metadata.next()