src/Pure/PIDE/headless.scala

         val already_committed1 =
           if (commit.isDefined) {
             (already_committed /: dep_theories)({ case (committed, name) =>
               def parents_committed: Boolean =
                 version.nodes(name).header.imports.forall({ case (parent, _) =>
-                  Sessions.is_pure(parent.theory) || committed.isDefinedAt(parent)
+                  resources.session_base.loaded_theory(parent) || committed.isDefinedAt(parent)
                 })
               if (!committed.isDefinedAt(name) && parents_committed &&
                   state.node_consolidated(version, name))
               {
                 val snapshot = stable_snapshot(state, version, name)