diff --git a/go.mod b/go.mod
index 1caec5e..37665ca 100644
--- a/go.mod
+++ b/go.mod
@@ -6,7 +6,7 @@ require (
 	golang.org/x/sync v0.6.0
 )
 
-require github.com/creachadair/mds v0.10.4
+require github.com/creachadair/mds v0.12.1
 
 go 1.21
 
diff --git a/go.sum b/go.sum
index 207e478..b7387fc 100644
--- a/go.sum
+++ b/go.sum
@@ -1,5 +1,5 @@
-github.com/creachadair/mds v0.10.4 h1:pYO7hGbXdgXGgTvgsRb8wC9Y0zJan7BQcHb3vqnQNIw=
-github.com/creachadair/mds v0.10.4/go.mod h1:4vrFYUzTXMJpMBU+OA292I6IUxKWCCfZkgXg+/kBZMo=
+github.com/creachadair/mds v0.12.1 h1:uJh5mwLcRMpoUVjrZUednb9bxxDPvD9+tt/TnuxIUUo=
+github.com/creachadair/mds v0.12.1/go.mod h1:4vrFYUzTXMJpMBU+OA292I6IUxKWCCfZkgXg+/kBZMo=
 github.com/fortytw2/leaktest v1.3.0 h1:u8491cBMTQ8ft8aeV+adlcytMZylmA5nnwwkRZjI8vw=
 github.com/fortytw2/leaktest v1.3.0/go.mod h1:jDsjWgpAGjm2CA7WthBh/CdZYEPF31XHquHwclZch5g=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
diff --git a/tools/go.mod b/tools/go.mod
index 1f3cffe..2cb938b 100644
--- a/tools/go.mod
+++ b/tools/go.mod
@@ -10,7 +10,7 @@ require (
 )
 
 require (
-	github.com/creachadair/mds v0.10.4 // indirect
+	github.com/creachadair/mds v0.12.1 // indirect
 	golang.org/x/sync v0.6.0 // indirect
 	nhooyr.io/websocket v1.8.10 // indirect
 )
diff --git a/tools/go.sum b/tools/go.sum
index dcede18..a16a5b5 100644
--- a/tools/go.sum
+++ b/tools/go.sum
@@ -1,7 +1,7 @@
 github.com/creachadair/jrpc2 v1.1.2 h1:UOYMipEFYlwd5qmcvs9GZBurn3oXt1UDIX5JLjWWFzo=
 github.com/creachadair/jrpc2 v1.1.2/go.mod h1:JcCe2Eny3lIvVwZLm92WXyU+tNUgTBWFCLMsfNkjEGk=
-github.com/creachadair/mds v0.10.4 h1:pYO7hGbXdgXGgTvgsRb8wC9Y0zJan7BQcHb3vqnQNIw=
-github.com/creachadair/mds v0.10.4/go.mod h1:4vrFYUzTXMJpMBU+OA292I6IUxKWCCfZkgXg+/kBZMo=
+github.com/creachadair/mds v0.12.1 h1:uJh5mwLcRMpoUVjrZUednb9bxxDPvD9+tt/TnuxIUUo=
+github.com/creachadair/mds v0.12.1/go.mod h1:4vrFYUzTXMJpMBU+OA292I6IUxKWCCfZkgXg+/kBZMo=
 github.com/creachadair/wschannel v0.0.0-20231211041550-f82e9bbfc258 h1:ylCT9u85Nxnsv6nSeye9CTWRtrzUm/nuwUMoVgW/VCw=
 github.com/creachadair/wschannel v0.0.0-20231211041550-f82e9bbfc258/go.mod h1:G2LDwAuE2B2YbCxMaxnB1qSC0Hzoy2Tf9eRel2qbRi8=
 github.com/fortytw2/leaktest v1.3.0 h1:u8491cBMTQ8ft8aeV+adlcytMZylmA5nnwwkRZjI8vw=