diff --git a/kindlecomicconverter/comic2ebook.py b/kindlecomicconverter/comic2ebook.py
index da6f5e52..3f2b5f88 100755
--- a/kindlecomicconverter/comic2ebook.py
+++ b/kindlecomicconverter/comic2ebook.py
@@ -746,7 +746,8 @@ def getPanelViewSize(deviceres, size):
 def sanitizeTree(filetree):
     chapterNames = {}
     for root, dirs, files in os.walk(filetree, False):
-        for i, name in enumerate(files):
+        # only iterate over original files before renaming
+        for i, name in list(enumerate(files)):
             splitname = os.path.splitext(name)
             newKey = os.path.join(root, f'{i:04}' + splitname[1])
             key = os.path.join(root, name)