diff -r 255dcbe53c50 -r d08f5b5ead0a src/HOL/Library/conditional_parametricity.ML
--- a/src/HOL/Library/conditional_parametricity.ML	Fri Apr 25 16:54:39 2025 +0200
+++ b/src/HOL/Library/conditional_parametricity.ML	Fri Apr 25 18:06:12 2025 +0200
@@ -110,7 +110,7 @@
 (* Tactics  *)
 (* helper tactics for printing *)
 fun error_tac ctxt msg st =
-  (error (msg ^ "\n" ^ Goal_Display.string_of_goal ctxt st); Seq.single st);
+  (error (Goal_Display.print_goal ctxt msg st); Seq.single st);
 
 fun error_tac' ctxt msg = SELECT_GOAL (error_tac ctxt msg);