diff --git a/gnu/usr.bin/groff/tmac/eqnrc b/gnu/usr.bin/groff/tmac/eqnrc
index eab720cf34da..fd064d1b40cd 100644
--- a/gnu/usr.bin/groff/tmac/eqnrc
+++ b/gnu/usr.bin/groff/tmac/eqnrc
@@ -50,6 +50,7 @@ ifdef ps|X ! set draw_lines 1 !
 
 ifdef ascii ! define n %1% !
 ifdef latin1 ! define n %1% !
+ifdef koi8-r ! define n %1% !
 ifdef n !
 set nroff 1
 !