diff --git a/programs/ssl/ssl_client2.c b/programs/ssl/ssl_client2.c
index 62d29ad..06e4a16 100644
--- a/programs/ssl/ssl_client2.c
+++ b/programs/ssl/ssl_client2.c
@@ -355,7 +355,7 @@
     pk_init( &pkey );
 #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 )