diff --git a/README.md b/README.md
index 1f57ab12950b527d0adfab4e959cf2837af39024..005f1fe15dcaefdbbcc23ca643137249dbd7e550 100644
--- a/README.md
+++ b/README.md
@@ -11,9 +11,18 @@ This package set has the following policy.
 * Non-versioned locations (git, unversioned tarballs) are permitted to allow
   GHC to advance.
 * The following packages must always build:
+  * plutus-ledger-api
   * plutus-tx
   * plutus-tx-plugin
 
+## Viewing Package Versions
+
+To see the full list of library versions in this repository, do.
+
+```
+nix flake show git+https://gitlab.horizon-haskell.net/package-sets/horizon-plutus
+```
+
 ## Updating the Package Set
 
 Generating the nix expressions for the package set is a two step process.