Index: apps/onplay.c
===================================================================
--- apps/onplay.c	(revision 13812)
+++ apps/onplay.c	(working copy)
@@ -589,6 +589,7 @@
     strncpy(newname, selected_file, sizeof newname);
     if (!kbd_input(newname + pathlen, (sizeof newname)-pathlen)) {
         if (!strlen(newname + pathlen) ||
+            (strrchr(newname, '/') + 1 - newname) > (ptr - selected_file) ||
             (rename(selected_file, newname) < 0)) {
             lcd_clear_display();
             lcd_puts(0,0,str(LANG_RENAME));