src/Pure/Thy/sessions.scala

--- a/src/Pure/Thy/sessions.scala	Wed Mar 30 21:16:22 2016 +0200
+++ b/src/Pure/Thy/sessions.scala	Wed Mar 30 21:33:48 2016 +0200
@@ -417,6 +417,6 @@
     def heap(name: String): Path =
       find_heap(name) getOrElse
         error("Unknown logic " + quote(name) + " -- no heap file found in:\n" +
-          cat_lines(input_dirs.map(dir => "  " + dir.implode)))
+          cat_lines(input_dirs.map(dir => "  " + dir.expand.implode)))
   }
 }