diff --git a/builder/main.py b/builder/main.py
index d9643f2..cc4d340 100644
--- a/builder/main.py
+++ b/builder/main.py
@@ -214,8 +214,9 @@ def _jlink_cmd_script(env, source):
     openocd_args.extend(
         debug_tools.get(upload_protocol).get("server").get("arguments", []))
     openocd_args.extend([
-        "-c", "program {$SOURCE} %s verify reset; shutdown;" %
-        board.get("upload.offset_address", "0x8000000")
+        "-c", "program %s %s verify reset; shutdown;" % (
+            env.subst(upload_source)[0].replace("\\", "/"), board.get(
+                "upload.offset_address", "0x8000000"))
     ])
     openocd_args = [
         f.replace("$PACKAGE_DIR",