diff --git a/include/util.h b/include/util.h
index f9e5685b24de601dcd510e36ee44c19f30dcb7b8..7d5ed9e628b521f1f34e188ae6ea6cf32e825c99 100644
--- a/include/util.h
+++ b/include/util.h
@@ -83,7 +83,7 @@ namespace util {
     std::vector<ROOT::Math::PxPyPzMVector> momenta{parts.size()};
     // transform our raw tracker info into proper 4-momenta
     std::transform(parts.begin(), parts.end(), momenta.begin(), [](const auto& part) {
-      eic::VectorXYZ p = part.p;
+      eic::VectorXYZ p = part.p();
       const double px = 0.;
       const double py = 0.;
       const double pz = 0.;