diff -r 85e8b4c2b9a9 -r c7051638a38c src/Pure/Thy/thy_header.scala
--- a/src/Pure/Thy/thy_header.scala	Mon Apr 04 23:46:14 2022 +0200
+++ b/src/Pure/Thy/thy_header.scala	Mon Apr 04 23:50:40 2022 +0200
@@ -151,8 +151,8 @@
           { case res => for ((as ~ (_ ~ bs)) <- res; a <- as; b <- bs) yield (a, b) }
 
       val args =
-        position(theory_name) ~
-        (opt($$$(IMPORTS) ~! rep1(position(theory_name))) ^^
+        position(this.theory_name) ~
+        (opt($$$(IMPORTS) ~! rep1(position(this.theory_name))) ^^
           { case None => Nil case Some(_ ~ xs) => xs }) ~
         (opt($$$(KEYWORDS) ~! keyword_decls) ^^
           { case None => Nil case Some(_ ~ xs) => xs }) ~