diff --git a/src/auth_action.rs b/src/auth_action.rs
index 40c7d9e..5b1dbd9 100644
--- a/src/auth_action.rs
+++ b/src/auth_action.rs
@@ -1,7 +1,7 @@
 use crate::configuration::{Action, FailureMode, Service};
 use crate::data::{store_metadata, Predicate, PredicateVec};
 use crate::envoy::{CheckResponse, CheckResponse_oneof_http_response, HeaderValueOption};
-use crate::service::{GrpcErrResponse, GrpcService};
+use crate::service::{GrpcErrResponse, GrpcService, Headers};
 use log::debug;
 use std::rc::Rc;
 
@@ -45,7 +45,7 @@ impl AuthAction {
     pub fn process_response(
         &self,
         check_response: CheckResponse,
-    ) -> Result<Vec<(String, String)>, GrpcErrResponse> {
+    ) -> Result<Headers, GrpcErrResponse> {
         //todo(adam-cattermole):hostvar resolver?
         // store dynamic metadata in filter state
         debug!("process_response(auth): store_metadata");
@@ -92,7 +92,7 @@ impl AuthAction {
         }
     }
 
-    fn get_header_vec(headers: &[HeaderValueOption]) -> Vec<(String, String)> {
+    fn get_header_vec(headers: &[HeaderValueOption]) -> Headers {
         headers
             .iter()
             .map(|header| {
diff --git a/src/filter/operations.rs b/src/filter/operations.rs
index 16206c5..0e62a29 100644
--- a/src/filter/operations.rs
+++ b/src/filter/operations.rs
@@ -1,6 +1,6 @@
 use crate::filter::operations::Operation::SendGrpcRequest;
 use crate::runtime_action_set::RuntimeActionSet;
-use crate::service::{GrpcErrResponse, GrpcRequest, IndexedGrpcRequest};
+use crate::service::{GrpcErrResponse, GrpcRequest, Headers, IndexedGrpcRequest};
 use std::rc::Rc;
 
 pub enum Operation {
@@ -86,15 +86,15 @@ impl GrpcMessageReceiverOperation {
 }
 
 pub struct HeadersOperation {
-    headers: Vec<(String, String)>,
+    headers: Headers,
 }
 
 impl HeadersOperation {
-    pub fn new(headers: Vec<(String, String)>) -> Self {
+    pub fn new(headers: Headers) -> Self {
         Self { headers }
     }
 
-    pub fn headers(self) -> Vec<(String, String)> {
+    pub fn headers(self) -> Headers {
         self.headers
     }
 }
diff --git a/src/ratelimit_action.rs b/src/ratelimit_action.rs
index 6d6fa0e..c8d6cf0 100644
--- a/src/ratelimit_action.rs
+++ b/src/ratelimit_action.rs
@@ -5,7 +5,7 @@ use crate::envoy::{
     HeaderValue, RateLimitDescriptor, RateLimitDescriptor_Entry, RateLimitResponse,
     RateLimitResponse_Code, StatusCode,
 };
-use crate::service::{GrpcErrResponse, GrpcService};
+use crate::service::{GrpcErrResponse, GrpcService, Headers};
 use cel_interpreter::Value;
 use log::{debug, error};
 use protobuf::RepeatedField;
@@ -206,7 +206,7 @@ impl RateLimitAction {
         }
     }
 
-    fn get_header_vec(headers: RepeatedField<HeaderValue>) -> Vec<(String, String)> {
+    fn get_header_vec(headers: RepeatedField<HeaderValue>) -> Headers {
         headers
             .iter()
             .map(|header| (header.key.to_owned(), header.value.to_owned()))
diff --git a/src/runtime_action.rs b/src/runtime_action.rs
index c9a4b9f..e2cbbc9 100644
--- a/src/runtime_action.rs
+++ b/src/runtime_action.rs
@@ -3,7 +3,7 @@ use crate::configuration::{Action, FailureMode, Service, ServiceType};
 use crate::ratelimit_action::RateLimitAction;
 use crate::service::auth::AuthService;
 use crate::service::rate_limit::RateLimitService;
-use crate::service::{GrpcErrResponse, GrpcService};
+use crate::service::{GrpcErrResponse, GrpcService, Headers};
 use log::debug;
 use protobuf::Message;
 use std::collections::HashMap;
@@ -67,7 +67,7 @@ impl RuntimeAction {
         }
     }
 
-    pub fn process_response(&self, msg: &[u8]) -> Result<Vec<(String, String)>, GrpcErrResponse> {
+    pub fn process_response(&self, msg: &[u8]) -> Result<Headers, GrpcErrResponse> {
         match self {
             Self::Auth(auth_action) => match Message::parse_from_bytes(msg) {
                 Ok(check_response) => auth_action.process_response(check_response),
diff --git a/src/runtime_action_set.rs b/src/runtime_action_set.rs
index e2a5837..584e3f1 100644
--- a/src/runtime_action_set.rs
+++ b/src/runtime_action_set.rs
@@ -1,7 +1,7 @@
 use crate::configuration::{ActionSet, Service};
 use crate::data::{Predicate, PredicateVec};
 use crate::runtime_action::RuntimeAction;
-use crate::service::{GrpcErrResponse, IndexedGrpcRequest};
+use crate::service::{GrpcErrResponse, Headers, IndexedGrpcRequest};
 use std::collections::HashMap;
 use std::rc::Rc;
 
@@ -80,7 +80,7 @@ impl RuntimeActionSet {
         &self,
         index: usize,
         msg: &[u8],
-    ) -> Result<(Option<IndexedGrpcRequest>, Vec<(String, String)>), GrpcErrResponse> {
+    ) -> Result<(Option<IndexedGrpcRequest>, Headers), GrpcErrResponse> {
         self.runtime_actions[index]
             .process_response(msg)
             .map(|headers| {
diff --git a/src/service.rs b/src/service.rs
index 7e0f036..cd88921 100644
--- a/src/service.rs
+++ b/src/service.rs
@@ -128,15 +128,16 @@ impl GrpcRequest {
     }
 }
 
+pub type Headers = Vec<(String, String)>;
 #[derive(Debug)]
 pub struct GrpcErrResponse {
     status_code: u32,
-    response_headers: Vec<(String, String)>,
+    response_headers: Headers,
     body: String,
 }
 
 impl GrpcErrResponse {
-    pub fn new(status_code: u32, response_headers: Vec<(String, String)>, body: String) -> Self {
+    pub fn new(status_code: u32, response_headers: Headers, body: String) -> Self {
         Self {
             status_code,
             response_headers,