diff --git a/RecoPixelVertexing/PixelVertexFinding/test/VertexFinder_t.h b/RecoPixelVertexing/PixelVertexFinding/test/VertexFinder_t.h
index 52253a1e4bbfe..5f8a0646c726a 100644
--- a/RecoPixelVertexing/PixelVertexFinding/test/VertexFinder_t.h
+++ b/RecoPixelVertexing/PixelVertexFinding/test/VertexFinder_t.h
@@ -67,9 +67,10 @@ struct ClusterGenerator {
     ev.ztrack.clear();
     ev.eztrack.clear();
     ev.ivert.clear();
+    ev.pttrack.clear();
     for (int iv = 0; iv < nclus; ++iv) {
       auto nt = trackGen(reng);
-      ev.itrack[nclus] = nt;
+      ev.itrack[iv] = nt;
       for (int it = 0; it < nt; ++it) {
         auto err = errgen(reng);  // reality is not flat....
         ev.ztrack.push_back(ev.zvert[iv] + err * gauss(reng));