diff --git a/setter/src/z80/filename.c b/setter/src/z80/filename.c
index 0d709e5..fd19fcd 100644
--- a/setter/src/z80/filename.c
+++ b/setter/src/z80/filename.c
@@ -51,7 +51,7 @@ void Filenames(const char* path)
         wRc = 0;
         cRc = 0;
 
-        if(!h) { rc = errno; }
+        if(!h) rc = errno != 0 ? errno : -1;
         else
         {
             ret = fprintf(h, FILENAME_FORMAT, filenames[pos]);