diff --git a/build.py b/build.py
index 1c6640c6..1a2d9748 100755
--- a/build.py
+++ b/build.py
@@ -37,6 +37,7 @@ log_lock = threading.Lock()
 def log(msg, mode=Hint):
     log_lock.acquire()
     print log_prefix[mode], msg
+    sys.stdout.flush()
     log_lock.release()