diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 9050edb..c89bf0c 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -488,7 +488,7 @@
 }
 
 static int ssl_parse_renegotiation_info( ssl_context *ssl,
-                                         unsigned char *buf,
+                                         const unsigned char *buf,
                                          size_t len )
 {
     int ret;
@@ -527,7 +527,7 @@
     return( 0 );
 }
 static int ssl_parse_max_fragment_length_ext( ssl_context *ssl,
-                                              unsigned char *buf,
+                                              const unsigned char *buf,
                                               size_t len )
 {
     /*