1 files changed, 2 insertions, 1 deletions

diff --git a/src/fileio.c b/src/fileio.c
index 6b9b9afb47c..bf592fa7c4d 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -260,7 +260,8 @@ report_file_error (string, data)
         break;
       default:
         /* System error messages are capitalized.  Downcase the initial
-           unless it is followed by a slash.  */
+           unless it is followed by a slash.  (The slash case caters to
+           error messages that begin with "I/O" or, in German, "E/A".)  */
         if (STRING_MULTIBYTE (errstring)
             && ! EQ (Faref (errstring, make_number (1)), make_number ('/')))
           {