diff --git a/runtime/doc/digraph.txt b/runtime/doc/digraph.txt
index 62f23a2..14a5676 100644
--- a/runtime/doc/digraph.txt
+++ b/runtime/doc/digraph.txt
@@ -111,11 +111,14 @@
 
 You may have problems using Vim with characters which have a value above 128.
 For example: You insert ue (u-umlaut) and the editor echoes \334 in Insert
-mode.  After leaving the Insert mode everything is fine.  Note that fmt
-removes all characters with a value above 128 from the text being formatted.
-On some Unix systems this means you have to define the environment-variable
-LC_CTYPE.  If you are using csh, then put the following line in your .cshrc: >
-	setenv LC_CTYPE iso_8859_1
+mode.  After leaving the Insert mode everything is fine.  On some Unix systems
+this means you have to define the environment-variable LC_CTYPE.  If you are
+using csh, then put the following line in your .cshrc: >
+	setenv LC_CTYPE en_US.utf8
+(or similar for a different language or country). The value must be a valid
+locale on your system, i.e. on Unix-like systems it must be present in the
+output of >
+	locale -a
 
 ==============================================================================
 3. Default digraphs					*digraphs-default*