diff --git a/arbitrile.cpp b/arbitrile.cpp
index 94d0f179..0ba5e9f2 100644
--- a/arbitrile.cpp
+++ b/arbitrile.cpp
@@ -513,6 +513,10 @@ EX void load(const string& fname, bool after_sliding IS(false)) {
     else if(ep.eat("treestate(")) {
       rulegen::parse_treestate(c, ep);
       }
+    else if(ep.eat("first_treestate(")) {
+      rulegen::rule_root = ep.iparse();
+      ep.force_eat(")");
+      }
     else if(ep.eat("yendor_backsteps(")) {
       c.yendor_backsteps = ep.iparse();
       ep.force_eat(")");
diff --git a/rulegen.cpp b/rulegen.cpp
index aa02fe94..c327b5b4 100644
--- a/rulegen.cpp
+++ b/rulegen.cpp
@@ -1620,10 +1620,8 @@ EX void parse_treestate(arb::arbi_tiling& c, exp_parser& ep) {
   }
 
 EX void verify_parsed_treestates() {
-  println(hlog, arb::current.shapes[0].connections);
-  println(hlog, arb::current.shapes[1].connections);
-  println(hlog, arb::current.shapes[0].stretch_shear);
-  for(auto& ts: treestates) println(hlog, ts.rules);
+  if(rule_root < 0 || rule_root >= isize(treestates))
+    throw hr_parse_exception("undefined treestate as root");
   for(auto& ts: treestates) for(auto& r: ts.rules) {
     if(r < 0 && !among(r, DIR_PARENT, DIR_LEFT, DIR_RIGHT))
       throw hr_parse_exception("negative number in treestates");