diff --git a/preprocessor/ComputingTasks.cc b/preprocessor/ComputingTasks.cc
index 134ea288e989fa7de8d67a20733863d76bf384cd..50922be8967ab46f2e26da2468d02ab2291f6c4e 100644
--- a/preprocessor/ComputingTasks.cc
+++ b/preprocessor/ComputingTasks.cc
@@ -1727,7 +1727,7 @@ EstimationDataStatement::writeOutput(ostream &output, const string &basename) co
 {
   options_list.writeOutput(output, "options_.dataset");
   if (options_list.date_options.find("first_obs") == options_list.date_options.end())
-    output << "options_.dataset.firstobs = options_.initial_period;" << endl;
+    output << "options_.dataset.first_obs = options_.initial_period;" << endl;
 }
 
 SubsamplesStatement::SubsamplesStatement(const string &name1_arg,