diff --git a/src/NumericalInitialization.cc b/src/NumericalInitialization.cc
index 1495fa36c4985874d8f9df64735795761292bb0d..27849afb5361c3be77dcb42c0b682991f3671e66 100644
--- a/src/NumericalInitialization.cc
+++ b/src/NumericalInitialization.cc
@@ -422,7 +422,7 @@ InitvalFileStatement::writeOutput(ostream &output, const string &basename, bool
          << "%" << endl
          << "options_.initval_file = true;" << endl;
   options_list.writeOutput(output, "options_initvalf");
-  output << "oo_.initval_series = initvalf(M_, options_initvalf);" << endl;
+  output << "[oo_.initval_series, options_.periods] = initvalf(M_, options_initvalf);" << endl;
 }
 
 void