diff --git a/calorimeters/simple_checking.cxx b/calorimeters/simple_checking.cxx
index 4d9dab192113dde6a042818c6d95e216aaa249d3..774317ffbacf23cc093a55b6d4afaf9fcf09727a 100644
--- a/calorimeters/simple_checking.cxx
+++ b/calorimeters/simple_checking.cxx
@@ -108,7 +108,7 @@ std::cout << "testing 3\n";
 std::cout << "testing 4\n";
   auto h0 = d1.Histo1D(TH1D("h0", "nhits; ", 20, 0,20), "nhits");
 
-  auto n0 = d1.Count();
+  auto n0 = d1.Filter([](int n){ return (n>=0); },{"nhits"}).Count();
 
   TCanvas* c = new TCanvas();