diff -r fcf5ee85743d -r 21a41356d78f src/Pure/GUI/gui.scala
--- a/src/Pure/GUI/gui.scala	Thu Jan 09 15:45:31 2020 +0100
+++ b/src/Pure/GUI/gui.scala	Thu Jan 09 16:01:31 2020 +0100
@@ -261,7 +261,7 @@
       "TextArea.font",
       "TextField.font",
       "TextPane.font",
-      "Tooltip.font",
+      "ToolTip.font",
       "Tree.font"))
     {
       val font = ui.get(prop) match { case font: Font => font case _ => default_font }