diff --git a/gateway-messages/src/sp_to_mgs.rs b/gateway-messages/src/sp_to_mgs.rs
index 8fbef08c..2fb46265 100644
--- a/gateway-messages/src/sp_to_mgs.rs
+++ b/gateway-messages/src/sp_to_mgs.rs
@@ -1233,6 +1233,7 @@ pub enum UpdateError {
     ImageMismatch,
     SignatureNotValidated,
     VersionNotSupported,
+    RollbackProtection,
 }
 
 impl fmt::Display for UpdateError {
@@ -1292,6 +1293,9 @@ impl fmt::Display for UpdateError {
             Self::InvalidComponent => {
                 write!(f, "invalid component for operation")
             }
+            Self::RollbackProtection => {
+                write!(f, "invalid epoch compared to active image")
+            }
         }
     }
 }
diff --git a/gateway-messages/tests/versioning/mod.rs b/gateway-messages/tests/versioning/mod.rs
index b9b737f2..484bc0a1 100644
--- a/gateway-messages/tests/versioning/mod.rs
+++ b/gateway-messages/tests/versioning/mod.rs
@@ -23,6 +23,7 @@ mod v14;
 mod v15;
 mod v16;
 mod v17;
+mod v18;
 
 pub fn assert_serialized<T: Serialize + SerializedSize + std::fmt::Debug>(
     expected: &[u8],
diff --git a/gateway-messages/tests/versioning/v18.rs b/gateway-messages/tests/versioning/v18.rs
new file mode 100644
index 00000000..ce7b90e8
--- /dev/null
+++ b/gateway-messages/tests/versioning/v18.rs
@@ -0,0 +1,36 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//! This source file is named after the protocol version being tested,
+//! e.g. v01.rs implements tests for protocol version 1.
+//! The tested protocol version is represented by "$VERSION" below.
+//!
+//! The tests in this module check that the serialized form of messages from MGS
+//! protocol version $VERSION have not changed.
+//!
+//! If a test in this module fails, _do not change the test_! This means you
+//! have changed, deleted, or reordered an existing message type or enum
+//! variant, and you should revert that change. This will remain true until we
+//! bump the `version::MIN` to a value higher than $VERSION, at which point these
+//! tests can be removed as we will stop supporting $VERSION.
+
+use super::assert_serialized;
+use gateway_messages::SerializedSize;
+use gateway_messages::SpResponse;
+use gateway_messages::UpdateError;
+
+#[test]
+fn error_enums() {
+    let mut out = [0; SpResponse::MAX_SIZE];
+
+    let response: [UpdateError; 5] = [
+        UpdateError::InvalidArchive,
+        UpdateError::ImageMismatch,
+        UpdateError::SignatureNotValidated,
+        UpdateError::VersionNotSupported,
+        UpdateError::RollbackProtection,
+    ];
+    let expected = vec![30, 31, 32, 33, 34];
+    assert_serialized(&mut out, &expected, &response);
+}