diff --git a/doc/dlb.6 b/doc/dlb.6
index d4557ae18..ca01bd8c7 100644
--- a/doc/dlb.6
+++ b/doc/dlb.6
@@ -152,5 +152,11 @@ Should include an optional compression facility.
 Not all read-only files for NetHack can be read out of an archive;
 examining the source is the only way to know which files can be.
 .SH COPYRIGHT
-This file is Copyright (C) \*(Na, \*(Nd for version \*(Nb:\*(Nr.
+.\" All troffs and nroffs support `\(co` except Plan 9 nroff, but Plan 9
+.\" offers no test for special character availability, and its feature
+.\" set too closely resembles DWB 3.3 to test for it.  Use a string with
+.\" any nroff-mode formatter not claiming groff compatiblity.
+.ds co \(co
+.if !\n(.g .if n .ds co (C)\" in principle, should be just "c"
+This file is Copyright \*(co \*(Na, \*(Nd for version \*(Nb:\*(Nr.
 NetHack may be freely redistributed.  See license for details.
diff --git a/doc/makedefs.6 b/doc/makedefs.6
index e2813adc8..1af27082f 100644
--- a/doc/makedefs.6
+++ b/doc/makedefs.6
@@ -272,5 +272,11 @@ end the most recent conditional
 .SH AUTHOR
 The NetHack Development Team
 .SH COPYRIGHT
-This file is Copyright (C) \*(Na, \*(Nd for version \*(Nb:\*(Nr.
+.\" All troffs and nroffs support `\(co` except Plan 9 nroff, but Plan 9
+.\" offers no test for special character availability, and its feature
+.\" set too closely resembles DWB 3.3 to test for it.  Use a string with
+.\" any nroff-mode formatter not claiming groff compatiblity.
+.ds co \(co
+.if !\n(.g .if n .ds co (C)\" in principle, should be just "c"
+This file is Copyright \*(co \*(Na, \*(Nd for version \*(Nb:\*(Nr.
 NetHack may be freely redistributed.  See license for details.
diff --git a/doc/nethack.6 b/doc/nethack.6
index 9e9fb97e0..290d56932 100644
--- a/doc/nethack.6
+++ b/doc/nethack.6
@@ -570,7 +570,13 @@ recover(6)
 .PP
 Probably infinite.
 .SH COPYRIGHT
-This file is Copyright (C) \*(Na, \*(Nd for version \*(Nb:\*(Nr.
+.\" All troffs and nroffs support `\(co` except Plan 9 nroff, but Plan 9
+.\" offers no test for special character availability, and its feature
+.\" set too closely resembles DWB 3.3 to test for it.  Use a string with
+.\" any nroff-mode formatter not claiming groff compatiblity.
+.ds co \(co
+.if !\n(.g .if n .ds co (C)\" in principle, should be just "c"
+This file is Copyright \*(co \*(Na, \*(Nd for version \*(Nb:\*(Nr.
 NetHack may be freely redistributed.  See license for details.
 .PP
 Dungeons & Dragons is a Trademark of Wizards of the Coast, Inc.
diff --git a/doc/recover.6 b/doc/recover.6
index 90d56c8c9..818ee18f1 100644
--- a/doc/recover.6
+++ b/doc/recover.6
@@ -148,5 +148,11 @@ determine.
 should be taught to use the nethack playground locking mechanism to
 avoid conflicts.
 .SH COPYRIGHT
-This file is Copyright (C) \*(Na, \*(Nd for version \*(Nb:\*(Nr.
+.\" All troffs and nroffs support `\(co` except Plan 9 nroff, but Plan 9
+.\" offers no test for special character availability, and its feature
+.\" set too closely resembles DWB 3.3 to test for it.  Use a string with
+.\" any nroff-mode formatter not claiming groff compatiblity.
+.ds co \(co
+.if !\n(.g .if n .ds co (C)\" in principle, should be just "c"
+This file is Copyright \*(co \*(Na, \*(Nd for version \*(Nb:\*(Nr.
 NetHack may be freely redistributed.  See license for details.