diff --git a/Cargo.toml b/Cargo.toml
index 532017f..c313057 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -8,7 +8,7 @@ categories = [ "science" ]
 license = "MIT OR Apache-2.0"
 name = "num-derive"
 repository = "https://github.com/rust-num/num-derive"
-version = "0.5.0"
+version = "0.5.1"
 readme = "README.md"
 exclude = ["/ci/*", "/.github/*"]
 edition = "2021"
diff --git a/README.md b/README.md
index b36c8ce..f8b0723 100644
--- a/README.md
+++ b/README.md
@@ -35,16 +35,6 @@ enum Color {
 }
 ```
 
-## Optional features
-
-- **`full-syntax`** — Enables `num-derive` to handle enum discriminants
-  represented by complex expressions. Usually can be avoided by
-  [utilizing constants], so only use this feature if namespace pollution is
-  undesired and [compile time doubling] is acceptable.
-
-[utilizing constants]: https://github.com/rust-num/num-derive/pull/3#issuecomment-359044704
-[compile time doubling]: https://github.com/rust-num/num-derive/pull/3#issuecomment-359172588
-
 ## Releases
 
 Release notes are available in [RELEASES.md](RELEASES.md).
diff --git a/RELEASES.md b/RELEASES.md
index dead040..ee2e3e4 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -1,3 +1,7 @@
+# Release 0.5.1 (2026-07-20)
+
+- Remove mention of the old "full-syntax" feature.
+
 # Release 0.5.0 (2026-07-20)
 
 - [Upgrade to `syn v3`.][71]