diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index b2b79cb..d3adbd0 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -3116,9 +3116,10 @@
 	because Vim cannot detect an error, thus the encoding is always
 	accepted.
 	The special value "default" can be used for the encoding from the
-	environment.  This is the default value for 'encoding'.  It is useful
-	when 'encoding' is set to "utf-8" and your environment uses a
-	non-latin1 encoding, such as Russian.
+	environment.  On MS-Windows this is the system encoding.  Otherwise
+	this is the default value for 'encoding'.  It is useful when
+	'encoding' is set to "utf-8" and your environment uses a non-latin1
+	encoding, such as Russian.
 	When 'encoding' is "utf-8" and a file contains an illegal byte
 	sequence it won't be recognized as UTF-8.  You can use the |8g8|
 	command to find the illegal byte sequence.