--- bin/9l.orig	2020-04-27 21:22:16 UTC
+++ bin/9l
@@ -14,7 +14,7 @@ case "$tag" in
 *DragonFly*|*BSD*)
 	ld=${CC9:-gcc}
 	userpath=true
-	extralibs="$extralibs -lutil"
+	extralibs="$extralibs -lutil -lpthread"
 	;;
 *OSF1*)
 	ld=${CC9:-cc}