diff --git a/packets.c b/packets.c
index ab1b095..d6de09a 100644
--- a/packets.c
+++ b/packets.c
@@ -85,7 +85,7 @@ int find_tls_ext_offset(uint16_t type, char *data, size_t size)
 }
 
 
-int change_tls_sni(char *host, char *buffer, size_t bsize)
+int change_tls_sni(const char *host, char *buffer, size_t bsize)
 {
     int sni_offs, pad_offs;
     
diff --git a/packets.h b/packets.h
index e16b80b..a52b6a6 100644
--- a/packets.h
+++ b/packets.h
@@ -13,7 +13,7 @@
 extern char tls_data[517];
 extern char http_data[43];
 
-int change_tls_sni(char *host, char *buffer, size_t bsize);
+int change_tls_sni(const char *host, char *buffer, size_t bsize);
 
 int parse_tls(char *buffer, size_t bsize, char **hs);