src/Pure/Thy/bibtex.scala

     val format_name: String = "bibtex"
     val file_ext: String = "bib"
 
     override def theory_suffix: String = "bibtex_file"
     override def theory_content(name: String): String =
-      """theory "bib" imports Pure begin bibtex_file """ + quote(name) + """ end"""
+      """theory "bib" imports Pure begin bibtex_file """ +
+        Outer_Syntax.quote_string(name) + """ end"""
 
     override def make_preview(snapshot: Document.Snapshot): Option[Presentation.Preview] =
     {
       val name = snapshot.node_name
       if (detect(name.node)) {