diff --git a/Cargo.toml b/Cargo.toml
index b59509a..34cfd32 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,6 +22,7 @@ http = { version = "1.0", default-features = false }
 async-trait = "0.1"
 axum = "0.7"                                         # TODO: remove
 tokio = { version = "1", features = ["sync"] }       # TODO: hide behind a feature?
+futures = "0.3"                                      # TODO
 
 # Optional dependencies required for the `guards` feature.
 tower = { version = "0.4", default-features = false, optional = true }
diff --git a/src/vary_middleware.rs b/src/vary_middleware.rs
index 2146643..84c614b 100644
--- a/src/vary_middleware.rs
+++ b/src/vary_middleware.rs
@@ -2,6 +2,7 @@ use std::sync::Arc;
 
 use axum::{extract::Request, middleware::Next, response::Response};
 use axum_core::response::IntoResponse;
+use futures::future::join_all;
 use http::{
     header::{HeaderValue, VARY},
     Extensions,
@@ -25,7 +26,7 @@ pub trait Notifier {
         }
     }
 
-    fn insert_into_extensions(extensions: &mut Extensions) -> Receiver<()>;
+    fn insert(extensions: &mut Extensions) -> Receiver<()>;
 }
 
 macro_rules! define_notifiers {
@@ -39,7 +40,7 @@ macro_rules! define_notifiers {
                     self.0.take().and_then(Arc::into_inner)
                 }
 
-                fn insert_into_extensions(extensions: &mut Extensions) -> Receiver<()> {
+                fn insert(extensions: &mut Extensions) -> Receiver<()> {
                     let (tx, rx) = oneshot::channel();
                     if extensions.insert(Self(Some(Arc::new(tx)))).is_some() {
                         panic!("{}", MIDDLEWARE_DOUBLE_USE);
@@ -59,36 +60,37 @@ define_notifiers!(
 );
 
 pub async fn vary_middleware(mut request: Request, next: Next) -> Response {
-    let hx_request_rx = HxRequestExtracted::insert_into_extensions(request.extensions_mut());
-    let hx_target_rx = HxTargetExtracted::insert_into_extensions(request.extensions_mut());
-    let hx_trigger_rx = HxTriggerExtracted::insert_into_extensions(request.extensions_mut());
-    let hx_trigger_name_rx =
-        HxTriggerNameExtracted::insert_into_extensions(request.extensions_mut());
+    let exts = request.extensions_mut();
+    let rx_header = [
+        (HxRequestExtracted::insert(exts), HX_REQUEST_STR),
+        (HxTargetExtracted::insert(exts), HX_TARGET_STR),
+        (HxTriggerExtracted::insert(exts), HX_TRIGGER_STR),
+        (HxTriggerNameExtracted::insert(exts), HX_TRIGGER_NAME_STR),
+    ];
 
     let mut response = next.run(request).await;
 
-    let mut used = Vec::with_capacity(4);
-    if hx_request_rx.await.is_ok() {
-        used.push(HX_REQUEST_STR)
-    }
-    if hx_target_rx.await.is_ok() {
-        used.push(HX_TARGET_STR)
-    }
-    if hx_trigger_rx.await.is_ok() {
-        used.push(HX_TRIGGER_STR)
-    }
-    if hx_trigger_name_rx.await.is_ok() {
-        used.push(HX_TRIGGER_NAME_STR)
+    let used_headers: Vec<_> = join_all(
+        rx_header
+            .into_iter()
+            .map(|(rx, header)| async move { rx.await.ok().map(|_| header) }),
+    )
+    .await
+    .into_iter()
+    .flatten()
+    .collect();
+
+    if used_headers.is_empty() {
+        return response;
     }
 
-    if !used.is_empty() {
-        let value = match HeaderValue::from_str(&used.join(", ")) {
-            Ok(x) => x,
-            Err(e) => return HxError::from(e).into_response(),
-        };
-        if let Err(e) = response.headers_mut().try_append(VARY, value) {
-            return HxError::from(e).into_response();
-        }
+    let value = match HeaderValue::from_str(&used_headers.join(", ")) {
+        Ok(x) => x,
+        Err(e) => return HxError::from(e).into_response(),
+    };
+
+    if let Err(e) = response.headers_mut().try_append(VARY, value) {
+        return HxError::from(e).into_response();
     }
 
     response