diff --git a/src/Pure/General/csv.scala b/src/Pure/General/csv.scala
--- a/src/Pure/General/csv.scala
+++ b/src/Pure/General/csv.scala
@@ -1,29 +1,29 @@
 /*  Title:      Pure/General/csv.scala
     Author:     Makarius
 
 Support for CSV: RFC 4180.
 */
 
 package isabelle
 
 
 object CSV {
   def print_field(field: Any): String = {
     val str = field.toString
-    if (str.exists("\",\r\n".contains(_))) {
+    if (str.exists("\",\r\n ".contains(_))) {
       (for (c <- str) yield { if (c == '"') "\"\"" else c.toString }).mkString("\"", "", "\"")
     }
     else str
   }
 
   sealed case class Record(fields: Any*) {
     override def toString: String = fields.iterator.map(print_field).mkString(",")
   }
 
   sealed case class File(name: String, header: List[String], records: List[Record]) {
     override def toString: String = (Record(header:_*) :: records).mkString("\r\n")
 
     def file_name: String = name + ".csv"
     def write(dir: Path): Unit = isabelle.File.write(dir + Path.explode(file_name), toString)
   }
 }