diff --git a/src/calibre/gui2/viewer/convert_book.py b/src/calibre/gui2/viewer/convert_book.py
index 85d756ff27..7907fefd9d 100644
--- a/src/calibre/gui2/viewer/convert_book.py
+++ b/src/calibre/gui2/viewer/convert_book.py
@@ -60,7 +60,7 @@ def robust_rmtree(x):
 
 
 def robust_rename(a, b):
-    retries = 10 if iswindows else 1  # retry on windows to get around the idiotic mandatory file locking
+    retries = 20 if iswindows else 1  # retry on windows to get around the idiotic mandatory file locking
     for i in range(retries):
         try:
             os.rename(a, b)