diff --git a/programs/ssl/ssl_server2.c b/programs/ssl/ssl_server2.c
index 48d5d30..f68eade 100644
--- a/programs/ssl/ssl_server2.c
+++ b/programs/ssl/ssl_server2.c
@@ -489,7 +489,7 @@
     ssl_cache_init( &cache );
 #endif
 #if defined(POLARSSL_SSL_ALPN)
-    memset( alpn_list, 0, sizeof alpn_list );
+    memset( (void *) alpn_list, 0, sizeof( alpn_list ) );
 #endif
 
     if( argc == 0 )