src/Pure/PIDE/headless.scala

--- a/src/Pure/PIDE/headless.scala	Sat Dec 05 11:49:04 2020 +0100
+++ b/src/Pure/PIDE/headless.scala	Sat Dec 05 12:14:40 2020 +0100
@@ -256,8 +256,8 @@
       val dep_theories = dependencies.theories
       val dep_theories_set = dep_theories.toSet
       val dep_files =
-        dependencies.loaded_files.flatMap(_._2).
-          map(path => Document.Node.Name(resources.append("", path)))
+        for (path <- dependencies.loaded_files)
+          yield Document.Node.Name(resources.append("", path))
 
       val use_theories_state =
       {