diff --git a/contrib/groff/tmac/doc-common b/contrib/groff/tmac/doc-common
index 7f7435d6542e..c2c899f1da43 100644
--- a/contrib/groff/tmac/doc-common
+++ b/contrib/groff/tmac/doc-common
@@ -90,6 +90,7 @@
 .nr Er 17n
 .nr Es 12n
 .nr Ev 15n
+.nr Ex 1
 .nr Fa 12n
 .nr Fc 3
 .nr Fd 12n\" ?