diff --git a/scripts/construct/build_pb.py b/scripts/construct/build_pb.py
index b77500f..a85ef1b 100644
--- a/scripts/construct/build_pb.py
+++ b/scripts/construct/build_pb.py
@@ -36,7 +36,7 @@ def need_rebuild(pb_files):
             return True
         s1 = os.stat(proto_name + '.pb.cc')
         s2 = os.stat('../tools/protobuild/' + proto_name + '.proto')
-        if s1.st_mtime < s2.st_mtime:
+        if s1.st_size <= 0 or s1.st_mtime < s2.st_mtime:
             return True
     return False