diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -27,3 +27,6 @@
 
 0.5.5.0, released 2025-11-28
     Bump cabal freeze
+
+0.5.5.1, released 2025-12-02
+    Revise README (reference to client)
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-This is a Haskell library for working with OpenTimestamps. OpenTimestamps is a protocol for creating and verifying timestamps for digital files, which can be used to prove that a file existed at a certain point in time.
+This is a Haskell library for working with OpenTimestamps. It's on Hackage here: [haskell-opentimestamps](https://hackage.haskell.org/package/haskell-opentimestamps). OpenTimestamps is a protocol for creating and verifying timestamps for digital files, which can be used to prove that a file existed at a certain point in time.
 
 The library provides functionality for:
 
@@ -14,3 +14,5 @@
 
 Notes on tests:
 * At least one of the tests requires a running local bitcoin node (pruned node is fine).
+
+There is also a client program that uses this library: It's on Hackage here: [haskell-opentimestamps-client](https://hackage.haskell.org/package/haskell-opentimestamps-client).
diff --git a/haskell-opentimestamps.cabal b/haskell-opentimestamps.cabal
--- a/haskell-opentimestamps.cabal
+++ b/haskell-opentimestamps.cabal
@@ -5,7 +5,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           haskell-opentimestamps
-version:        0.5.5.0
+version:        0.5.5.1
 synopsis:       Haskell implementation of OpenTimestamps
 description:    Please see the README on Codeberg at <https://codeberg.org/photonsphere/haskell-opentimestamps#readme>
 category:       Bitcoin, Finance, Network, Cryptography
diff --git a/package.yaml b/package.yaml
--- a/package.yaml
+++ b/package.yaml
@@ -1,5 +1,5 @@
 name:                haskell-opentimestamps
-version:             0.5.5.0
+version:             0.5.5.1
 license:             BSD3
 #x-license:           BSD-3-Clause OR Apache-2.0
 git:                 "https://codeberg.org/photonsphere/haskell-opentimestamps"
diff --git a/src/OpenTimestamps/Config.hs b/src/OpenTimestamps/Config.hs
--- a/src/OpenTimestamps/Config.hs
+++ b/src/OpenTimestamps/Config.hs
@@ -34,7 +34,7 @@
 
 -- | User-Agent string for HTTP requests.
 userAgent :: ByteString
-userAgent = "Haskell-OpenTimestamps-Client/0.5.5.0"
+userAgent = "Haskell-OpenTimestamps-Client/0.5.5.1"
 
 -- | URL string for digest HTTP requests.
 apiUrlDigest :: String