diff --git a/specfile/constants.py b/specfile/constants.py
index 5b16686..505271c 100644
--- a/specfile/constants.py
+++ b/specfile/constants.py
@@ -96,9 +96,11 @@
     "buildarch",
     "buildarchitectures",
     "buildconflicts",
+    "buildoption",
     "buildprereq",
     "buildrequires",
     "buildroot",
+    "buildsystem",
     "conflicts",
     "distribution",
     "disttag",