diff --git a/crpptbx/gdat.m b/crpptbx/gdat.m
index bd2c03f081a466c7ba559d2ec927f0c4a2f5be22..64692c2fe94fbbcc95f69bafc50c02cb4994f7ce 100644
--- a/crpptbx/gdat.m
+++ b/crpptbx/gdat.m
@@ -166,6 +166,7 @@ try
 catch
   warning(['problems calling gdat_' lower(machine_eff)]);
   if ~exist('gdat_data'); gdat_data.data = []; end
+  if  ~isfield(gdat_data,'dim'); gdat_data.dim=[]; end
   if ~exist('gdat_params'); gdat_params.plot = []; end
   if ~exist('error_status'); error_status = 998; end
   return