diff --git a/programs/pkey/dh_server.c b/programs/pkey/dh_server.c
index 8bf2b1b29f..7906ac1b83 100644
--- a/programs/pkey/dh_server.c
+++ b/programs/pkey/dh_server.c
@@ -234,6 +234,7 @@ int main( void )
 
     memset( buf, 0, sizeof( buf ) );
 
+    n = dhm.len;
     if( ( ret = mbedtls_net_recv( &client_fd, buf, n ) ) != (int) n )
     {
         mbedtls_printf( " failed\n  ! mbedtls_net_recv returned %d\n\n", ret );