diff --git a/Fonderie/fifo.c b/Fonderie/fifo.c
index 8de0bde..47f925a 100644
--- a/Fonderie/fifo.c
+++ b/Fonderie/fifo.c
@@ -51,6 +51,11 @@ fprintf(stderr, ">>> %s ( %p %p %d )\n", __func__,
 				pfifo, destination, step);
 #endif
 
+if (step<1){
+	fprintf(stderr, "***** %s invalid step %d\n", __func__, step);
+	exit(1);
+	}
+
 if (NULL==destination) {
 	pdest = &(pfifo->total);		}
 else	{
@@ -68,11 +73,11 @@ for (idx=0; idx<pfifo->nbslots; idx += step) {
 		}
 	}
 
-/* XXX
+#if 0
 fprintf(stderr, "*** %s:%s writing debugB file ***\n",
 			__FILE__, __func__);
 fimg_dump_to_file(&g_fifo.total, "debugB.fimg", 0);
-XXX */
+#endif
 
 return 0;
 }
@@ -96,6 +101,10 @@ if (foo) {
 	return foo;
 	}
 
+#if 0
+	fimg_dump_to_file(&g_fifo.total, "outputXXX.fimg", 0);
+#endif
+
 foo = fimg_export_picture(&g_fifo.total, fname, 0);
 if (foo) {
 	fprintf(stderr, "ERR EXPORT '%s' is %d\n", fname, foo);