diff --git a/MC/config/examples/epos4/generator/NeNe_536TeV_EPOS4.optns b/MC/config/examples/epos4/generator/NeNe_536TeV_EPOS4.optns
index 9c7df71a3..5c84f533d 100644
--- a/MC/config/examples/epos4/generator/NeNe_536TeV_EPOS4.optns
+++ b/MC/config/examples/epos4/generator/NeNe_536TeV_EPOS4.optns
@@ -29,4 +29,5 @@ set nfreeze 1            !number of freeze out events per hydro event
 set modsho 1             !printout every modsho events
 set centrality 0         !0=min bias
 set ihepmc 2             !HepMC output enabled on stdout
+fillTree4(C1)            !C1 sets impact parameter as centrality variable
 set nfull 10
diff --git a/MC/config/examples/epos4/generator/OO_536TeV_EPOS4.optns b/MC/config/examples/epos4/generator/OO_536TeV_EPOS4.optns
index 254a1e4a4..eeaab8cd9 100644
--- a/MC/config/examples/epos4/generator/OO_536TeV_EPOS4.optns
+++ b/MC/config/examples/epos4/generator/OO_536TeV_EPOS4.optns
@@ -29,4 +29,5 @@ set nfreeze 1            !number of freeze out events per hydro event
 set modsho 1             !printout every modsho events
 set centrality 0         !0=min bias
 set ihepmc 2             !HepMC output enabled on stdout
+fillTree4(C1)            !C1 sets impact parameter as centrality variable
 set nfull 10
diff --git a/MC/config/examples/epos4/generator/examplepbpb.optns b/MC/config/examples/epos4/generator/examplepbpb.optns
index 217b2db77..49a41c350 100644
--- a/MC/config/examples/epos4/generator/examplepbpb.optns
+++ b/MC/config/examples/epos4/generator/examplepbpb.optns
@@ -29,4 +29,5 @@ set nfreeze 1            !number of freeze out events per hydro event
 set modsho 1             !printout every modsho events
 set centrality 0         !0=min bias
 set ihepmc 2             !HepMC output enabled on stdout
+fillTree4(C1)            !C1 sets impact parameter as centrality variable
 set nfull 10
\ No newline at end of file