diff --git a/quiche/include/quiche.h b/quiche/include/quiche.h
index 014150d9aa..c518705860 100644
--- a/quiche/include/quiche.h
+++ b/quiche/include/quiche.h
@@ -402,17 +402,17 @@ void quiche_conn_peer_cert(quiche_conn *conn, const uint8_t **out, size_t *out_l
 void quiche_conn_session(quiche_conn *conn, const uint8_t **out, size_t *out_len);
 
 // Returns true if the connection handshake is complete.
-bool quiche_conn_is_established(quiche_conn *conn);
+bool quiche_conn_is_established(const quiche_conn *conn);
 
 // Returns true if the connection has a pending handshake that has progressed
 // enough to send or receive early data.
-bool quiche_conn_is_in_early_data(quiche_conn *conn);
+bool quiche_conn_is_in_early_data(const quiche_conn *conn);
 
 // Returns whether there is stream or DATAGRAM data available to read.
-bool quiche_conn_is_readable(quiche_conn *conn);
+bool quiche_conn_is_readable(const quiche_conn *conn);
 
 // Returns true if the connection is draining.
-bool quiche_conn_is_draining(quiche_conn *conn);
+bool quiche_conn_is_draining(const quiche_conn *conn);
 
 // Returns the number of bidirectional streams that can be created
 // before the peer's stream count limit is reached.
@@ -423,10 +423,10 @@ uint64_t quiche_conn_peer_streams_left_bidi(quiche_conn *conn);
 uint64_t quiche_conn_peer_streams_left_uni(quiche_conn *conn);
 
 // Returns true if the connection is closed.
-bool quiche_conn_is_closed(quiche_conn *conn);
+bool quiche_conn_is_closed(const quiche_conn *conn);
 
 // Returns true if the connection was closed due to the idle timeout.
-bool quiche_conn_is_timed_out(quiche_conn *conn);
+bool quiche_conn_is_timed_out(const quiche_conn *conn);
 
 // Returns true if a connection error was received, and updates the provided
 // parameters accordingly.
diff --git a/quiche/src/ffi.rs b/quiche/src/ffi.rs
index 4418974b34..784fa7ecb3 100644
--- a/quiche/src/ffi.rs
+++ b/quiche/src/ffi.rs
@@ -987,27 +987,27 @@ pub extern fn quiche_conn_session(
 }
 
 #[no_mangle]
-pub extern fn quiche_conn_is_established(conn: &mut Connection) -> bool {
+pub extern fn quiche_conn_is_established(conn: &Connection) -> bool {
     conn.is_established()
 }
 
 #[no_mangle]
-pub extern fn quiche_conn_is_in_early_data(conn: &mut Connection) -> bool {
+pub extern fn quiche_conn_is_in_early_data(conn: &Connection) -> bool {
     conn.is_in_early_data()
 }
 
 #[no_mangle]
-pub extern fn quiche_conn_is_draining(conn: &mut Connection) -> bool {
+pub extern fn quiche_conn_is_draining(conn: &Connection) -> bool {
     conn.is_draining()
 }
 
 #[no_mangle]
-pub extern fn quiche_conn_is_closed(conn: &mut Connection) -> bool {
+pub extern fn quiche_conn_is_closed(conn: &Connection) -> bool {
     conn.is_closed()
 }
 
 #[no_mangle]
-pub extern fn quiche_conn_is_timed_out(conn: &mut Connection) -> bool {
+pub extern fn quiche_conn_is_timed_out(conn: &Connection) -> bool {
     conn.is_timed_out()
 }