diff --git a/matlab/@ucf/ucf.m b/matlab/@ucf/ucf.m
index 2d1da1f..c5dd890 100644
--- a/matlab/@ucf/ucf.m
+++ b/matlab/@ucf/ucf.m
@@ -213,7 +213,7 @@ classdef ucf < handle
       % ? endian          endianess {'n' (dafault),'a','l','s','b'}
       par = inputParser;
       addOptional(par,'type','field',@ischar);
-      addOptional(par,'rank',[0,0,0,0],@(x)isnumeric(x)&&numel(x)==4);
+      addOptional(par,'rank',[0,0,0,0],@(x)(isnumeric(x)&&numel(x)==4));
       addOptional(par,'endian','n',@ischar);
       parse(par,varargin{:});
       %
diff --git a/matlab/write_particles_ucf.m b/matlab/write_particles_ucf.m
index 41959cd..61240cc 100644
--- a/matlab/write_particles_ucf.m
+++ b/matlab/write_particles_ucf.m
@@ -6,10 +6,9 @@ function [] = write_particles_ucf(file,pp,col,time,varargin)
     %   pp                  particle data in 'array' format with dim(ncol,np,nt)
     %   col                 particle column map. CAUTION: data is not rearranged according to colmap yet!!!
     %   time                simulation time with dim(nt)
-    % Optional input (key/value pair)
-    %   endian              endianess of the file as used by fopen (default: 'n')
-    %   verbosity           verbose output? (default: no)
-    %   debug               debug output? (default: no)
+    % ? endian              endianess of the file as used by fopen (default: 'n')
+    % ? verbosity           verbose output? (default: no)
+    % ? debug               debug output? (default: no)
 
     % Parse variable input
     par = inputParser;