diff --git a/MC/CustomGenerators/PWGUD/Starlight_flat_rho.C b/MC/CustomGenerators/PWGUD/Starlight_flat_rho.C
new file mode 100644
index 00000000..d3dd14f4
--- /dev/null
+++ b/MC/CustomGenerators/PWGUD/Starlight_flat_rho.C
@@ -0,0 +1,9 @@
+AliGenerator* GeneratorCustom() {
+  AliGenerator* gen = GeneratorStarlight();
+  if (processConfig == TString("kCohRhoToPiFlat")) {
+    AliGenStarLight *genStarLight = (AliGenStarLight*) gen;
+    // set maximum invariant mass for pipi system to 4 GeV/c^2 (2 GeV/c^2 by default)
+    genStarLight->SetParameter("W_MAX        =   4.0    #Max value of w");
+  }
+  return gen;
+}