diff -r d80b2df54d31 -r a96320074298 src/HOL/Library/Code_Prolog.thy
--- a/src/HOL/Library/Code_Prolog.thy	Sun Jan 06 13:44:33 2019 +0100
+++ b/src/HOL/Library/Code_Prolog.thy	Sun Jan 06 15:04:34 2019 +0100
@@ -9,7 +9,7 @@
 keywords "values_prolog" :: diag
 begin
 
-ML_file "~~/src/HOL/Tools/Predicate_Compile/code_prolog.ML"
+ML_file \<open>~~/src/HOL/Tools/Predicate_Compile/code_prolog.ML\<close>
 
 section \<open>Setup for Numerals\<close>