diff --git a/src/calibre/utils/copy_files.py b/src/calibre/utils/copy_files.py
index 856ff79704..a0aa55fcf7 100644
--- a/src/calibre/utils/copy_files.py
+++ b/src/calibre/utils/copy_files.py
@@ -21,7 +21,8 @@ WindowsFileId = Tuple[int, int, int]
 
 class UnixFileCopier:
 
-    def __init__(self):
+    def __init__(self, delete_all=False):
+        self.delete_all = delete_all
         self.copy_map: Dict[str, str] = {}
 
     def register(self, path: str, dest: str) -> None:
@@ -30,8 +31,9 @@ class UnixFileCopier:
     def __enter__(self) -> None:
         pass
 
-    def __exit__(self, *a) -> None:
-        pass
+    def __exit__(self, exc_type, exc_val, exc_tb) -> None:
+        if self.delete_all and exc_val is None:
+            self.delete_all_source_files()
 
     def rename_all(self) -> None:
         for src_path, dest_path in self.copy_map.items():
@@ -57,7 +59,8 @@ class WindowsFileCopier:
     Locks all files before starting the copy, ensuring other processes cannot interfere
     '''
 
-    def __init__(self):
+    def __init__(self, delete_all=False):
+        self.delete_all = delete_all
         self.path_to_fileid_map : Dict[str, WindowsFileId] = {}
         self.fileid_to_paths_map: Dict[WindowsFileId, Set[str]] = defaultdict(set)
         self.path_to_handle_map: Dict[str, 'winutil.Handle'] = {}
@@ -98,9 +101,13 @@ class WindowsFileCopier:
         for src in self.copy_map:
             self.path_to_handle_map[src] = self._open_file(src)
 
-    def __exit__(self, *a) -> None:
-        for h in self.path_to_handle_map.values():
-            h.close()
+    def __exit__(self, exc_type, exc_val, exc_tb) -> None:
+        try:
+            if self.delete_all and exc_val is None:
+                self.delete_all_source_files()
+        finally:
+            for h in self.path_to_handle_map.values():
+                h.close()
 
     def copy_all(self) -> None:
         for src_path, dest_path in self.copy_map.items():
@@ -128,8 +135,8 @@ class WindowsFileCopier:
             winutil.delete_file(make_long_path_useable(src_path))
 
 
-def get_copier() -> Union[UnixFileCopier, WindowsFileCopier]:
-    return WindowsFileCopier() if iswindows else UnixFileCopier()
+def get_copier(delete_all=False) -> Union[UnixFileCopier, WindowsFileCopier]:
+    return WindowsFileCopier(delete_all) if iswindows else UnixFileCopier(delete_all)
 
 
 def rename_files(src_to_dest_map: Dict[str, str]) -> None:
@@ -142,14 +149,12 @@ def rename_files(src_to_dest_map: Dict[str, str]) -> None:
 
 
 def copy_files(src_to_dest_map: Dict[str, str], delete_source: bool = False) -> None:
-    copier = get_copier()
+    copier = get_copier(delete_source)
     for s, d in src_to_dest_map.items():
         if not samefile(s, d):
             copier.register(s, d)
     with copier:
         copier.copy_all()
-        if delete_source:
-            copier.delete_all_source_files()
 
 
 def copy_tree(
@@ -183,7 +188,7 @@ def copy_tree(
         return os.path.join(dest_dir, rel)
 
 
-    copier = get_copier()
+    copier = get_copier(delete_source)
     for (dirpath, dirnames, filenames) in os.walk(src, onerror=raise_error):
         for d in dirnames:
             path = os.path.join(dirpath, d)
@@ -205,8 +210,6 @@ def copy_tree(
 
     with copier:
         copier.copy_all()
-        if delete_source:
-            copier.delete_all_source_files()
 
     if delete_source:
         try: