diff --git a/src/pspm_extract_segments.m b/src/pspm_extract_segments.m
index 4af2e5549..0b8e32a4d 100644
--- a/src/pspm_extract_segments.m
+++ b/src/pspm_extract_segments.m
@@ -91,15 +91,20 @@
 % check consistency of input for the other methods
 if strcmpi(method, 'file') % in this case use pspm_check_model to verify
     channel = varargin{1};
-    model = pspm_check_model( ...
-        struct('modelfile', 'dummyfile.mat', ...
+    model = struct('modelfile', 'dummyfile.mat', ...
                    'datafile', data, ...
                    'timing', timing, ...
-                   'timeunits', options.timeunits), ...
-                   'glm');
+                   'timeunits', options.timeunits);
+    if isfield(options, 'missing')
+        model.missing = options.missing;
+    end
+    model = pspm_check_model(model, 'glm');
     if model.invalid, return; end
     timing = model.timing;
     datafile = model.datafile;
+    if isfield(options, 'missing')
+        options.missing =  model.missing;
+    end
 elseif strcmpi(method, 'data') % verify directly
    sr = varargin{1};
    if isnumeric(data)
@@ -213,8 +218,6 @@
     if sts < 1, return; end
 end
 
-
-
 if options.plot
   fg = figure('Name', 'Condition mean per subject', 'Visible', 'off');
   ax = axes('NextPlot', 'add');
diff --git a/src/pspm_pp.m b/src/pspm_pp.m
index d6c52cb81..e777d706d 100644
--- a/src/pspm_pp.m
+++ b/src/pspm_pp.m
@@ -2,7 +2,7 @@
 % ● Description
 %   pspm_pp contains various preprocessing utilities for reducing noise in 
 %   the data. It features a 'butter' option that allows downsampling after 
-%   application of an anti-alias filter.
+%   application of an anti-alias filter.  
 % ● Format
 %   [sts, fn] = pspm_pp('median', fn, channel, n,    options) or
 %   [sts, fn] = pspm_pp('butter', fn, channel, filt, options) or
@@ -11,7 +11,8 @@
 %        method:  [string] Method of filtering. Currently implemented
 %                 methods are 'median' and 'butter'. (1) 'median': a median
 %                 filter will be applied. (2) 'butter': Butterworth band
-%                 pass filter potentially including downsampling.
+%                 pass filter potentially including downsampling; any NaN
+%                 data are interpolated before filtering and then removed
 %                 (3) 'leaky_integrator': Applies a leaky integrator filter
 %                 where tau is specified in seconds.
 %            fn:  [string] The datafile that saves data to process