diff --git a/usr.bin/sed/sed.1 b/usr.bin/sed/sed.1
index e724e114b0c2..55eb36a52162 100644
--- a/usr.bin/sed/sed.1
+++ b/usr.bin/sed/sed.1
@@ -505,6 +505,19 @@ This is the same as specifying the
 .Fl n
 option on the command line.
 .El
+.Sh ENVIRONMENT
+The following environment variables affect the execution of
+.Nm :
+.Bl -tag -width ".Ev COLUMNS"
+.It Ev COLUMNS
+If set, specifies the user's preferred output width in column positions.
+The
+.Dq l
+command uses this value to fold long lines to an appropriate width.
+By default,
+.Nm
+attempts to automatically determine the terminal width.
+.El
 .Sh DIAGNOSTICS
 .Ex -std
 .Sh SEE ALSO