diff --git a/xfibresoptions.h b/xfibresoptions.h
index 1acb003d04b7e758d76119e770cd5db68a5f2b62..f65e29b9f57f78a05dc0ad71d8583e936465c596 100644
--- a/xfibresoptions.h
+++ b/xfibresoptions.h
@@ -52,7 +52,7 @@ class xfibresOptions {
   Option<bool> rician;
   Option<bool> f0;
   Option<bool> ardf0;
-  Option<string> grad_file;
+  FmribOption<string> grad_file;
 
   void parse_command_line(int argc, char** argv,  Log& logger);