diff --git a/filesetup.c b/filesetup.c
index fa09219..bf05b6f 100644
--- a/filesetup.c
+++ b/filesetup.c
@@ -806,7 +806,7 @@
 	 * Calculate per-file size and potential extra size for the
 	 * first files, if needed.
 	 */
-	if (!o->file_size_low) {
+	if (!o->file_size_low && o->nr_files) {
 		uint64_t all_fs;
 
 		fs = o->size / o->nr_files;