Index: ../trunk-jpl/src/c/classes/IoModel.cpp
===================================================================
--- ../trunk-jpl/src/c/classes/IoModel.cpp	(revision 23577)
+++ ../trunk-jpl/src/c/classes/IoModel.cpp	(revision 23578)
@@ -453,8 +453,8 @@
 	int *types = NULL;
 
 	/*Initialize array detecting whether data[i] is an independent AD mode variable: */
-	this->FetchData(&autodiff,"md.autodiff.isautodiff");
-	this->FetchData(&iscontrol,"md.inversion.iscontrol");
+	this->FetchConstants(&autodiff,"md.autodiff.isautodiff");
+	this->FetchConstants(&iscontrol,"md.inversion.iscontrol");
 
 	if(trace || (autodiff && !iscontrol)){
 
@@ -2536,6 +2536,9 @@
 	if(strncmp(data_name,mddot,3)!=0){
 		_error_("Cannot fetch \""<<data_name<<"\" does not start with \""<<mddot<<"\"");
 	}
+	if(fid==NULL){
+		_error_("Cannot fetch \""<<data_name<<"\": file pointer invalid ");
+	}
 
 	/*Go find in the binary file, the position of the data we want to fetch: */
 	if(my_rank==0){