diff --git a/vcg/complex/algorithms/clean.h b/vcg/complex/algorithms/clean.h
index d025aa76..7d2e806c 100644
--- a/vcg/complex/algorithms/clean.h
+++ b/vcg/complex/algorithms/clean.h
@@ -75,6 +75,7 @@ public:
 
   void start(MeshType &m, FacePointer p)
   {
+    tri::RequirePerFaceMark(m);
     mp=&m;
     while(!sf.empty()) sf.pop();
     UnMarkAll(m);