diff --git a/src/Params.h b/src/Params.h
index 23970a1..b7eafee 100644
--- a/src/Params.h
+++ b/src/Params.h
@@ -39,8 +39,8 @@ namespace cafmaker
     fhicl::OptionalAtom<std::string> tmsRecoFile  { fhicl::Name{"TMSRecoFile"}, fhicl::Comment("Input TMS reco .root file") };
     fhicl::OptionalAtom<std::string> sandRecoFile  { fhicl::Name{"SANDRecoFile"}, fhicl::Comment("Input SAND reco .root file") };
 
-    // this is optional, will result in an extra output file if enabled
-    fhicl::OptionalAtom<bool> makeFlatCAF { fhicl::Name({"MakeFlatCAF"}), fhicl::Comment("Make 'flat' CAF in addition to structured CAF?") };
+    // this is optional by way of the default value. Will result in an extra output file if enabled
+    fhicl::Atom<bool> makeFlatCAF { fhicl::Name{"MakeFlatCAF"}, fhicl::Comment("Make 'flat' CAF in addition to structured CAF?"), true };
 
     // these are optional and have defaults
     fhicl::Atom<int>  first   { fhicl::Name("FirstEvt"), fhicl::Comment("Start processing from this event number"), 0 };