src/Pure/GUI/gui.scala

--- a/src/Pure/GUI/gui.scala	Thu Mar 02 15:46:27 2017 +0100
+++ b/src/Pure/GUI/gui.scala	Thu Mar 02 15:56:43 2017 +0100
@@ -262,7 +262,7 @@
   def install_fonts()
   {
     val ge = GraphicsEnvironment.getLocalGraphicsEnvironment()
-    for (font <- Path.split(Isabelle_System.getenv_strict("ISABELLE_FONTS")))
+    for (font <- Isabelle_System.fonts())
       ge.registerFont(Font.createFont(Font.TRUETYPE_FONT, font.file))
   }
 }