diff --git a/src/core/mainloop/connection.c b/src/core/mainloop/connection.c
index 92755914ec..79e034fb34 100644
--- a/src/core/mainloop/connection.c
+++ b/src/core/mainloop/connection.c
@@ -250,13 +250,13 @@ CONST_TO_LISTENER_CONN(const connection_t *c)
 }
 
 size_t
-connection_get_inbuf_len(connection_t *conn)
+connection_get_inbuf_len(const connection_t *conn)
 {
   return conn->inbuf ? buf_datalen(conn->inbuf) : 0;
 }
 
 size_t
-connection_get_outbuf_len(connection_t *conn)
+connection_get_outbuf_len(const connection_t *conn)
 {
     return conn->outbuf ? buf_datalen(conn->outbuf) : 0;
 }
diff --git a/src/core/mainloop/connection.h b/src/core/mainloop/connection.h
index 36c94d6570..8b378b15a4 100644
--- a/src/core/mainloop/connection.h
+++ b/src/core/mainloop/connection.h
@@ -274,8 +274,8 @@ void connection_buf_add_compress(const char *string, size_t len,
                                  struct dir_connection_t *conn, int done);
 void connection_buf_add_buf(struct connection_t *conn, struct buf_t *buf);
 
-size_t connection_get_inbuf_len(struct connection_t *conn);
-size_t connection_get_outbuf_len(struct connection_t *conn);
+size_t connection_get_inbuf_len(const struct connection_t *conn);
+size_t connection_get_outbuf_len(const struct connection_t *conn);
 struct connection_t *connection_get_by_global_id(uint64_t id);
 
 struct connection_t *connection_get_by_type(int type);