diff --git a/builder/main.py b/builder/main.py
index 1a4642e..323ef90 100644
--- a/builder/main.py
+++ b/builder/main.py
@@ -150,6 +150,8 @@ def _parseSdccFlags(flags):
             stcgal_protocol,
             "-p",
             "$UPLOAD_PORT",
+            "-b",
+            "$UPLOAD_SPEED",
             "-t",
             int(f_cpu_khz),
             "-a",