diff --git a/libfreefare/mifare_desfire.c b/libfreefare/mifare_desfire.c
index a28f5b4..03242c4 100644
--- a/libfreefare/mifare_desfire.c
+++ b/libfreefare/mifare_desfire.c
@@ -1268,7 +1268,7 @@ create_file1 (MifareTag tag, uint8_t command, uint8_t file_no, int has_iso_file_
 
     BUFFER_APPEND (cmd, command);
     BUFFER_APPEND (cmd, file_no);
-    if (iso_file_id >= 0)
+    if (iso_file_id)
 	BUFFER_APPEND_LE (cmd, iso_file_id, sizeof (iso_file_id), sizeof (iso_file_id));
     BUFFER_APPEND (cmd, communication_settings);
     BUFFER_APPEND_LE (cmd, access_rights, 2, sizeof (uint16_t));