diff --git a/gnu/usr.bin/groff/tmac/mdoc.local b/gnu/usr.bin/groff/tmac/mdoc.local
index a3073ff7d8d..ffd931007e3 100644
--- a/gnu/usr.bin/groff/tmac/mdoc.local
+++ b/gnu/usr.bin/groff/tmac/mdoc.local
@@ -58,6 +58,7 @@
 .ds doc-str-Lb-libpmc      Performance Monitoring Counters Interface Library (libpmc, \-lpmc)
 .ds doc-str-Lb-librpcsec_gss RPC GSS-API Authentication Library (librpcsec_gss, \-lrpcsec_gss)
 .ds doc-str-Lb-librpcsvc   RPC Service Library (librpcsvc, \-lrpcsvc)
+.ds doc-str-lb-librtld_db  Run-time Linker Debugging Library (librtld_db, \-lrtld_db)
 .ds doc-str-Lb-libsdp      Bluetooth Service Discovery Protocol User Library (libsdp, \-lsdp)
 .ds doc-str-Lb-libthr      1:1 Threading Library (libthr, \-lthr)
 .ds doc-str-Lb-libufs      UFS File System Access Library (libufs, \-lufs)