diff --git a/programs/ssl/ssl_server.c b/programs/ssl/ssl_server.c
index fc1f4ed..78d9065 100644
--- a/programs/ssl/ssl_server.c
+++ b/programs/ssl/ssl_server.c
@@ -87,7 +87,7 @@
     int listen_fd;
     int client_fd = -1;
     unsigned char buf[1024];
-    char *pers = "ssl_server";
+    const char *pers = "ssl_server";
 
     entropy_context entropy;
     ctr_drbg_context ctr_drbg;
@@ -118,7 +118,7 @@
      * Instead, you may want to use x509parse_crtfile() to read the
      * server and CA certificates, as well as x509parse_keyfile().
      */
-    ret = x509parse_crt( &srvcert, (unsigned char *) test_srv_crt,
+    ret = x509parse_crt( &srvcert, (const unsigned char *) test_srv_crt,
                          strlen( test_srv_crt ) );
     if( ret != 0 )
     {
@@ -126,7 +126,7 @@
         goto exit;
     }
 
-    ret = x509parse_crt( &srvcert, (unsigned char *) test_ca_crt,
+    ret = x509parse_crt( &srvcert, (const unsigned char *) test_ca_crt,
                          strlen( test_ca_crt ) );
     if( ret != 0 )
     {
@@ -135,7 +135,7 @@
     }
 
     rsa_init( &rsa, RSA_PKCS_V15, 0 );
-    ret =  x509parse_key( &rsa, (unsigned char *) test_srv_key,
+    ret =  x509parse_key( &rsa, (const unsigned char *) test_srv_key,
                           strlen( test_srv_key ), NULL, 0 );
     if( ret != 0 )
     {
@@ -167,7 +167,8 @@
 
     entropy_init( &entropy );
     if( ( ret = ctr_drbg_init( &ctr_drbg, entropy_func, &entropy,
-                               (unsigned char *) pers, strlen( pers ) ) ) != 0 )
+                               (const unsigned char *) pers,
+                               strlen( pers ) ) ) != 0 )
     {
         printf( " failed\n  ! ctr_drbg_init returned %d\n", ret );
         goto exit;