diff --git a/crpptbx/TCV/gdat_tcv.m b/crpptbx/TCV/gdat_tcv.m
index 03cdaf098c76f3af08adfc2c160df99f08eb871d..e230a8d9bec4fed912e842d927ee5b1712791da0 100644
--- a/crpptbx/TCV/gdat_tcv.m
+++ b/crpptbx/TCV/gdat_tcv.m
@@ -559,7 +559,11 @@ elseif strcmp(mapping_for_tcv.method,'expression')
       end
     end
     gdat_data.data_fullpath=mapping_for_tcv.expression;
-    gdat_data.help = gdat_tmp.help;
+    if isfield(gdat_tmp,'help')
+      gdat_data.help = gdat_tmp.help;
+    else
+      gdat_data.help = [];
+    end
   end
   % end of method "expression"