diff --git a/serprog.c b/serprog.c
index 65bb5b0..24a51ac 100644
--- a/serprog.c
+++ b/serprog.c
@@ -300,7 +300,8 @@
 		return 1;
 	}
 	sp[0] = cmd;
-	memcpy(&(sp[1]), parms, parmlen);
+	if (parms)
+		memcpy(&(sp[1]), parms, parmlen);
 
 	if (sp_streamed_transmit_bytes >= (1 + parmlen + sp_device_serbuf_size)) {
 		if (sp_flush_stream() != 0) {