diff --git a/docs/manual.rst b/docs/manual.rst
index 16d44e874..364a62499 100644
--- a/docs/manual.rst
+++ b/docs/manual.rst
@@ -2643,7 +2643,9 @@ source directory and the target directory.
 overwrite. If it would, it will fail. Otherwise it will proceed as if it was in
 ``always_replace_files`` mode. Note that there is an inherent race condition here.
 If the files in the target directory appear after the check but before the copy
-or move completes, they will be overwritten.
+or move completes, they will be overwritten. When failing because of files already
+existing in the target path, the ``error`` of ``move_storage_failed_alert`` is set
+to ``boost::system::errc::file_exists``.
 
 The intention is that a client may use this as a probe, and if it fails, ask the user
 which mode to use. The client may then re-issue the ``move_storage`` call with one
diff --git a/src/disk_io_thread.cpp b/src/disk_io_thread.cpp
index 21a1a4691..6cec6a167 100644
--- a/src/disk_io_thread.cpp
+++ b/src/disk_io_thread.cpp
@@ -2241,7 +2241,14 @@ namespace libtorrent
 #endif
 					TORRENT_ASSERT(j.buffer == 0);
 					ret = j.storage->move_storage_impl(j.str, j.piece);
-					if (ret != 0)
+					if (ret != piece_manager::file_exist)
+					{
+						j.error = error_code(boost::system::errc::file_exists, get_system_category());
+						j.error_file = -1;
+						j.buffer = NULL;
+						break;
+					}
+					if (ret != piece_manager::no_error && ret != piece_manager::need_full_check)
 					{
 						test_error(j);
 						break;