diff --git a/Cargo.lock b/Cargo.lock
index d9bed7b62..3ce6610bd 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -6088,7 +6088,7 @@ dependencies = [
 
 [[package]]
 name = "zcash_protocol"
-version = "0.3.0"
+version = "0.4.0"
 dependencies = [
  "document-features",
  "incrementalmerkletree",
diff --git a/Cargo.toml b/Cargo.toml
index 2fb0c99c0..1df798ed8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -36,7 +36,7 @@ zcash_address = { version = "0.5", path = "components/zcash_address" }
 zcash_client_backend = { version = "0.13", path = "zcash_client_backend" }
 zcash_encoding = { version = "0.2.1", path = "components/zcash_encoding" }
 zcash_keys = { version = "0.3", path = "zcash_keys" }
-zcash_protocol = { version = "0.3", path = "components/zcash_protocol" }
+zcash_protocol = { version = "0.4", path = "components/zcash_protocol" }
 zip321 = { version = "0.1", path = "components/zip321" }
 
 zcash_note_encryption = "0.4"
diff --git a/components/zcash_protocol/CHANGELOG.md b/components/zcash_protocol/CHANGELOG.md
index 207db86e8..505c8408a 100644
--- a/components/zcash_protocol/CHANGELOG.md
+++ b/components/zcash_protocol/CHANGELOG.md
@@ -7,6 +7,7 @@ and this library adheres to Rust's notion of
 
 ## [Unreleased]
 
+## [0.4.0] - 2024-10-02
 ### Added
 - `impl Sub<BlockHeight> for BlockHeight` unlike the implementation that was
   removed in version `0.3.0`, a saturating subtraction for block heights having
diff --git a/components/zcash_protocol/Cargo.toml b/components/zcash_protocol/Cargo.toml
index e093916d9..5424e16cb 100644
--- a/components/zcash_protocol/Cargo.toml
+++ b/components/zcash_protocol/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "zcash_protocol"
 description = "Zcash protocol network constants and value types."
-version = "0.3.0"
+version = "0.4.0"
 authors = [
     "Jack Grigg <jack@electriccoin.co>",
     "Kris Nuttycombe <kris@nutty.land>",
diff --git a/supply-chain/imports.lock b/supply-chain/imports.lock
index 3e348bf63..4a9090bb7 100644
--- a/supply-chain/imports.lock
+++ b/supply-chain/imports.lock
@@ -1,6 +1,10 @@
 
 # cargo-vet imports lock
 
+[[unpublished.zcash_protocol]]
+version = "0.4.0"
+audited_as = "0.3.0"
+
 [[publisher.bumpalo]]
 version = "3.16.0"
 when = "2024-04-08"
diff --git a/zcash_client_backend/CHANGELOG.md b/zcash_client_backend/CHANGELOG.md
index 817054d19..61a02654a 100644
--- a/zcash_client_backend/CHANGELOG.md
+++ b/zcash_client_backend/CHANGELOG.md
@@ -13,7 +13,7 @@ and this library adheres to Rust's notion of
   - `WalletSummary::recovery_progress`
 
 ### Changed
-- Migrated to `orchard 0.10`, `sapling-crypto 0.3`.
+- Migrated to `orchard 0.10`, `sapling-crypto 0.3`, `zcash_protocol 0.4`.
 - The `Account` trait now uses an associated type for its `AccountId`
   type instead of a type parameter. This change allows for the simplification
   of some type signatures.
diff --git a/zcash_client_sqlite/CHANGELOG.md b/zcash_client_sqlite/CHANGELOG.md
index 0dc86e47d..fcc550c0e 100644
--- a/zcash_client_sqlite/CHANGELOG.md
+++ b/zcash_client_sqlite/CHANGELOG.md
@@ -8,7 +8,7 @@ and this library adheres to Rust's notion of
 ## [Unreleased]
 
 ### Changed
-- Migrated to `orchard 0.10`, `sapling-crypto 0.3`.
+- Migrated to `orchard 0.10`, `sapling-crypto 0.3`, `zcash_protocol 0.4`.
 - `zcash_client_sqlite::error::SqliteClientError::RequestedRewindInvalid`
   is now a structured variant.
 
diff --git a/zcash_keys/CHANGELOG.md b/zcash_keys/CHANGELOG.md
index 2dcc873fb..007944d2a 100644
--- a/zcash_keys/CHANGELOG.md
+++ b/zcash_keys/CHANGELOG.md
@@ -13,7 +13,7 @@ and this library adheres to Rust's notion of
 - `impl std::error::Error for DerivationError`
 
 ### Changed
-- Migrated to `orchard 0.10`, `sapling-crypto 0.3`.
+- Migrated to `orchard 0.10`, `sapling-crypto 0.3`, `zcash_protocol 0.4`.
 
 ## [0.3.0] - 2024-08-19
 ### Notable changes
diff --git a/zcash_primitives/CHANGELOG.md b/zcash_primitives/CHANGELOG.md
index fdd77368b..b617d284e 100644
--- a/zcash_primitives/CHANGELOG.md
+++ b/zcash_primitives/CHANGELOG.md
@@ -9,7 +9,7 @@ and this library adheres to Rust's notion of
 
 ### Changed
 - Update dependencies to `incrementalmerkletree 0.7`, `orchard 0.10`,
-  `sapling-crypto 0.3`.
+  `sapling-crypto 0.3`, `zcash_protocol 0.4`.
 
 ## [0.17.0] - 2024-08-26