diff --git a/fsl_regfilt.cc b/fsl_regfilt.cc
index e97434fb5468e24b270caf3b79ac24ae2f5e55bc..675d4cbcd8e96ea56959a25bec3b38df78bf8e60 100644
--- a/fsl_regfilt.cc
+++ b/fsl_regfilt.cc
@@ -36,7 +36,7 @@ using namespace std;
 		string("output file name for the filtered data"),
 		true, requires_argument);
   Option<string> fndesign(string("-d,--design"), string(""),
-		string("file name of the GLM design matrix (time courses)"),
+		string("file name of the matrix with time courses (e.g. GLM design or MELODIC mixing matrix)"),
 		true, requires_argument);
   Option<string> fnmask(string("-m,--mask"), string(""),
 		string("mask image file name"),