diff --git a/matlab/bvar_toolbox.m b/matlab/bvar_toolbox.m
index 061b13bf0b0db130d335d341eaa067fed19dee5a..9131ae5fee8553c54618fe167161b5b6067a0157 100644
--- a/matlab/bvar_toolbox.m
+++ b/matlab/bvar_toolbox.m
@@ -69,7 +69,7 @@ function [ny, nx, posterior, prior, forecast_data] = bvar_toolbox(nlags)
         dataset = log(dataset);
     end
     if options_.prefilter
-        dataset = dataset(idx,:) - ones(length(idx),1)*mean(dataset(idx,:));
+        dataset(idx,:) = dataset(idx,:) - ones(length(idx),1)*mean(dataset(idx,:));
     end
     
     mnprior.tight = options_.bvar_prior_tau;