diff --git a/core/lib/src/request/request.rs b/core/lib/src/request/request.rs
index c281b5575c..1e7f6181e8 100644
--- a/core/lib/src/request/request.rs
+++ b/core/lib/src/request/request.rs
@@ -307,7 +307,7 @@ impl<'r> Request<'r> {
     /// Ideally, this will match the `Host` header in the request.
     #[cfg(feature = "tls")]
     #[inline(always)]
-    pub fn sni(&mut self) -> Option<&str> {
+    pub fn sni(&self) -> Option<&str> {
         self.connection.server_name.as_deref()
     }