diff -r d80b2df54d31 -r a96320074298 src/HOL/Transitive_Closure.thy
--- a/src/HOL/Transitive_Closure.thy	Sun Jan 06 13:44:33 2019 +0100
+++ b/src/HOL/Transitive_Closure.thy	Sun Jan 06 15:04:34 2019 +0100
@@ -12,7 +12,7 @@
     and "^=" = "\<^sup>=" "\<^sup>=\<^sup>="
 begin
 
-ML_file "~~/src/Provers/trancl.ML"
+ML_file \<open>~~/src/Provers/trancl.ML\<close>
 
 text \<open>
   \<open>rtrancl\<close> is reflexive/transitive closure,