diff --git a/autoninja.py b/autoninja.py
index 8e69ceb83..0d3ba701e 100755
--- a/autoninja.py
+++ b/autoninja.py
@@ -187,7 +187,7 @@ def _print_cmd(cmd):
     print(*[shell_quoter(arg) for arg in cmd], file=sys.stderr)
 
 
-def _main_inner(input_args, should_collect_logs=False):
+def _main_inner(input_args, build_id, should_collect_logs=False):
     # if user doesn't set PYTHONPYCACHEPREFIX and PYTHONDONTWRITEBYTECODE
     # set PYTHONDONTWRITEBYTECODE=1 not to create many *.pyc in workspace
     # and keep workspace clean.
@@ -277,6 +277,8 @@ def _main_inner(input_args, should_collect_logs=False):
                     file=sys.stderr,
                 )
                 return 1
+            # Build ID consistently used in other tools. e.g. Reclient, ninjalog.
+            os.environ.setdefault("SISO_BUILD_ID", build_id)
             if use_remoteexec:
                 if use_reclient:
                     return reclient_helper.run_siso(
@@ -428,7 +430,7 @@ def main(args):
     if sys.platform.startswith("win") and len(args) == 2:
         input_args = args[:1] + args[1].split()
     try:
-        exit_code = _main_inner(input_args, should_collect_logs)
+        exit_code = _main_inner(input_args, build_id, should_collect_logs)
     except KeyboardInterrupt:
         exit_code = 1
     finally: