diff --git a/http-signature-normalization-warp/src/digest/mod.rs b/http-signature-normalization-warp/src/digest/mod.rs
index 9ad7caa..edb4308 100644
--- a/http-signature-normalization-warp/src/digest/mod.rs
+++ b/http-signature-normalization-warp/src/digest/mod.rs
@@ -35,16 +35,13 @@ pub enum ParseDigestError {
 #[error("Could not parse request body")]
 pub struct ParseBodyError;
 
-pub fn verify_digest_bytes<D>(
-    verifier: impl Filter<Extract = (D,), Error = Rejection> + Clone,
-) -> impl Filter<Extract = (Bytes,), Error = Rejection> + Clone
-where
-    D: DigestVerify + Send,
-{
-    verifier
-        .and(parse_digest_header())
+pub fn verify_digest_bytes(
+    verifier: impl DigestVerify + Clone + Send,
+) -> impl Filter<Extract = (Bytes,), Error = Rejection> + Clone {
+    parse_digest_header()
         .and(body::bytes())
-        .and_then(|mut verifier: D, parts: Vec<DigestPart>, bytes: Bytes| {
+        .and_then(move |parts: Vec<DigestPart>, bytes: Bytes| {
+            let mut verifier = verifier.clone();
             async move {
                 if verifier.verify(&parts, &bytes) {
                     Ok(bytes)
@@ -55,11 +52,10 @@ where
         })
 }
 
-pub fn verify_digest_json<D, T>(
-    verifier: impl Filter<Extract = (D,), Error = Rejection> + Clone,
+pub fn verify_digest_json<T>(
+    verifier: impl DigestVerify + Clone + Send
 ) -> impl Filter<Extract = (T,), Error = Rejection> + Clone
 where
-    D: DigestVerify + Send,
     T: serde::de::DeserializeOwned,
 {
     verify_digest_bytes(verifier).and_then(|bytes: Bytes| {
@@ -69,11 +65,10 @@ where
     })
 }
 
-pub fn verify_digest_form<D, T>(
-    verifier: impl Filter<Extract = (D,), Error = Rejection> + Clone,
+pub fn verify_digest_form<T>(
+    verifier: impl DigestVerify + Clone + Send,
 ) -> impl Filter<Extract = (T,), Error = Rejection> + Clone
 where
-    D: DigestVerify + Send,
     T: serde::de::DeserializeOwned,
 {
     verify_digest_bytes(verifier).and_then(|bytes: Bytes| {