diff -r 8f0b2daa7eaa -r d93ead9ac6df src/HOL/Orderings.thy
--- a/src/HOL/Orderings.thy	Thu Jun 12 08:03:05 2025 +0200
+++ b/src/HOL/Orderings.thy	Thu Jun 12 12:44:47 2025 +0200
@@ -653,8 +653,8 @@
 end
 
 setup \<open>
-  map_theory_simpset (fn ctxt0 => ctxt0 addSolver
-    mk_solver "partial and linear orders" (fn ctxt => HOL_Order_Tac.tac (Simplifier.prems_of ctxt) ctxt))
+  map_theory_simpset (fn ctxt0 => ctxt0 |> Simplifier.add_unsafe_solver
+    (mk_solver "partial and linear orders" (fn ctxt => HOL_Order_Tac.tac (Simplifier.prems_of ctxt) ctxt)))
 \<close>
 
 ML \<open>