diff --git a/common/ssl_calls.c b/common/ssl_calls.c
index b305815f..30640c51 100644
--- a/common/ssl_calls.c
+++ b/common/ssl_calls.c
@@ -140,7 +140,7 @@ ssl_rc4_info_delete(void *rc4_info)
 
 /*****************************************************************************/
 void
-ssl_rc4_set_key(void *rc4_info, char *key, int len)
+ssl_rc4_set_key(void *rc4_info, const char *key, int len)
 {
     RC4_set_key((RC4_KEY *)rc4_info, len, (tui8 *)key);
 }
@@ -214,7 +214,7 @@ ssl_md5_clear(void *md5_info)
 
 /*****************************************************************************/
 void
-ssl_md5_transform(void *md5_info, char *data, int len)
+ssl_md5_transform(void *md5_info, const char *data, int len)
 {
     MD5_Update((MD5_CTX *)md5_info, data, len);
 }
diff --git a/common/ssl_calls.h b/common/ssl_calls.h
index 121cb390..78edd946 100644
--- a/common/ssl_calls.h
+++ b/common/ssl_calls.h
@@ -31,7 +31,7 @@ ssl_rc4_info_create(void);
 void
 ssl_rc4_info_delete(void *rc4_info);
 void
-ssl_rc4_set_key(void *rc4_info, char *key, int len);
+ssl_rc4_set_key(void *rc4_info, const char *key, int len);
 void
 ssl_rc4_crypt(void *rc4_info, char *data, int len);
 void *
@@ -51,7 +51,7 @@ ssl_md5_info_delete(void *md5_info);
 void
 ssl_md5_clear(void *md5_info);
 void
-ssl_md5_transform(void *md5_info, char *data, int len);
+ssl_md5_transform(void *md5_info, const char *data, int len);
 void
 ssl_md5_complete(void *md5_info, char *data);
 void *