diff --git a/atomicfile_test.go b/atomicfile_test.go
index 8eff238..d9dc593 100644
--- a/atomicfile_test.go
+++ b/atomicfile_test.go
@@ -10,7 +10,7 @@ import (
 	"testing"
 
 	"github.com/creachadair/atomicfile"
-	"github.com/creachadair/mtest"
+	"github.com/creachadair/mds/mtest"
 )
 
 var (
diff --git a/go.mod b/go.mod
index 4013c83..62a3026 100644
--- a/go.mod
+++ b/go.mod
@@ -4,4 +4,4 @@ go 1.21
 
 toolchain go1.21.6
 
-require github.com/creachadair/mtest v0.0.0-20231015022703-31f2ea539dce
+require github.com/creachadair/mds v0.13.3
diff --git a/go.sum b/go.sum
index 711ec28..acc8ffe 100644
--- a/go.sum
+++ b/go.sum
@@ -1,2 +1,2 @@
-github.com/creachadair/mtest v0.0.0-20231015022703-31f2ea539dce h1:BFjvg2Oq88/2DOcUFu1ScIwKUn7KJYYvLr6AeuCJD54=
-github.com/creachadair/mtest v0.0.0-20231015022703-31f2ea539dce/go.mod h1:okn1ft6DY+qjPmnvYynyq7ufIQKJ2x2qwOCJZecei1k=
+github.com/creachadair/mds v0.13.3 h1:OqXNRorXKsuvfjor+0ixtrpA4IINApH8zgm23XLlngk=
+github.com/creachadair/mds v0.13.3/go.mod h1:4vrFYUzTXMJpMBU+OA292I6IUxKWCCfZkgXg+/kBZMo=