diff --git a/src/PenningTrap.cpp b/src/PenningTrap.cpp
index 23e1b80..83b7be7 100644
--- a/src/PenningTrap.cpp
+++ b/src/PenningTrap.cpp
@@ -31,7 +31,7 @@ PenningTrap::PenningTrap(double B_0, double V_0, double d)
 
 void PenningTrap::add_particle(Particle particle)
 {
-
+    this->particles.push_back(particle);
 }
 
 arma::vec PenningTrap::external_E_field(arma::vec r)