src/HOL/ROOT

--- a/src/HOL/ROOT	Mon Jun 08 22:49:06 2020 +0200
+++ b/src/HOL/ROOT	Tue Jun 09 12:13:15 2020 +0100
@@ -20,6 +20,7 @@
   sessions
     "HOL-Library"
   theories
+    Ackermann
     Knaster_Tarski
     Peirce
     Drinker