diff --git a/crates/sip-auth/src/digest.rs b/crates/sip-auth/src/digest.rs
index 7132993..2e9d5f1 100644
--- a/crates/sip-auth/src/digest.rs
+++ b/crates/sip-auth/src/digest.rs
@@ -8,15 +8,15 @@ use sip_types::header::typed::{
 use sip_types::print::{AppendCtx, PrintCtx, UriContext};
 
 pub struct DigestCredentials {
-    user: String,
-    password: String,
+    user: BytesStr,
+    password: BytesStr,
 }
 
 impl DigestCredentials {
     pub fn new<U, P>(user: U, password: P) -> Self
     where
-        U: Into<String>,
-        P: Into<String>,
+        U: Into<BytesStr>,
+        P: Into<BytesStr>,
     {
         Self {
             user: user.into(),