1 files changed, 1 insertions, 1 deletions
diff --git a/utils/chi2 b/utils/chi2
index 6e41f16..24bd9cd 100755
--- a/utils/chi2
+++ b/utils/chi2
@@ -525,7 +525,7 @@ if __name__ == '__main__':
     ev_mcs = []
     for filename in args.mc:
         ev_mcs.append(get_events([filename], merge_fits=True, nhit_thresh=args.nhit_thresh, mc=True))
-    ev_mc = pd.concat(ev_mcs).reset_index()
+    ev_mc = pd.concat([ev_mc for ev_mc in ev_mcs if len(ev_mc) > 0]).reset_index()
     muon_mc = get_events(args.muon_mc, merge_fits=True, nhit_thresh=args.nhit_thresh, mc=True)
     weights = pd.concat([read_hdf(filename, "weights") for filename in args.weights],ignore_index=True)