diff -r ce844442e2ab -r 11dc8929832d src/Pure/Thy/sessions.scala
--- a/src/Pure/Thy/sessions.scala	Thu Jul 23 11:48:58 2020 +0200
+++ b/src/Pure/Thy/sessions.scala	Thu Jul 23 14:25:48 2020 +0200
@@ -715,12 +715,12 @@
 
     def build_selection(sel: Selection): List[String] = selected(build_graph, sel)
     def build_descendants(ss: List[String]): List[String] = build_graph.all_succs(ss)
-    def build_requirements(ss: List[String]): List[String] = build_graph.all_preds(ss).reverse
+    def build_requirements(ss: List[String]): List[String] = build_graph.all_preds_rev(ss)
     def build_topological_order: List[String] = build_graph.topological_order
 
     def imports_selection(sel: Selection): List[String] = selected(imports_graph, sel)
     def imports_descendants(ss: List[String]): List[String] = imports_graph.all_succs(ss)
-    def imports_requirements(ss: List[String]): List[String] = imports_graph.all_preds(ss).reverse
+    def imports_requirements(ss: List[String]): List[String] = imports_graph.all_preds_rev(ss)
     def imports_topological_order: List[String] = imports_graph.topological_order
 
     override def toString: String =