diff --git a/include/PenningTrap.hpp b/include/PenningTrap.hpp
index 1b1752e..3601634 100644
--- a/include/PenningTrap.hpp
+++ b/include/PenningTrap.hpp
@@ -13,9 +13,13 @@
 #define __PENNING_TRAP__
 
 #include <armadillo>
+#include <omp.h>
 
-#include "constants.hpp"
 #include "Particle.hpp"
+#include "constants.hpp"
+
+#pragma omp declare reduction( + : arma::vec : omp_out += omp_in ) \
+  initializer( omp_priv = omp_orig )
 
 /** @brief A class that simulates a Penning trap.
  *
diff --git a/src/PenningTrap.cpp b/src/PenningTrap.cpp
index 59be75c..eeb0c0d 100644
--- a/src/PenningTrap.cpp
+++ b/src/PenningTrap.cpp
@@ -13,15 +13,9 @@
  *  @todo Implement evolve_forward_euler
  * */
 
-#include "utils.hpp"
 #include "PenningTrap.hpp"
 #include "constants.hpp"
-#include <algorithm>
-#include <stdexcept>
-#include <omp.h>
-
-#pragma omp declare reduction( + : arma::vec : omp_out += omp_in ) \
-  initializer( omp_priv = omp_orig )
+#include "utils.hpp"
 
 PenningTrap::PenningTrap(double B_0, double V_0, double d)
 {