diff --git a/src/MC/fix_charge_regulation.cpp b/src/MC/fix_charge_regulation.cpp
index 6226dd5ba5..416d0541c3 100644
--- a/src/MC/fix_charge_regulation.cpp
+++ b/src/MC/fix_charge_regulation.cpp
@@ -42,6 +42,7 @@
 
 #include <cmath>
 #include <cstring>
+#include <memory>
 
 using namespace LAMMPS_NS;
 using namespace FixConst;
@@ -724,7 +725,9 @@ void FixChargeRegulation::forward_ions_multival() {
   double energy_before = energy_stored;
   double factor = 1;
   double dummyp[3];
-  int mm[salt_charge_ratio + 1];// particle ID array for all ions to be inserted
+
+  // particle ID array for all ions to be inserted
+  auto mm = std::unique_ptr<int[]>(new int[salt_charge_ratio + 1]);
 
   if (salt_charge[0] <= -salt_charge[1]) {
     // insert one anion and (salt_charge_ratio) cations
@@ -778,9 +781,12 @@ void FixChargeRegulation::backward_ions_multival() {
   double energy_before = energy_stored;
   double factor = 1;
   double dummyp[3];  // dummy particle
-  int mm[salt_charge_ratio + 1];  // particle ID array for all deleted ions
-  double qq[salt_charge_ratio + 1];  // charge array for all deleted ions
-  int mask_tmp[salt_charge_ratio + 1];  // temporary mask array
+  // particle ID array for all deleted ions
+  auto mm = std::unique_ptr<int[]>(new int[salt_charge_ratio + 1]);
+  // charge array for all deleted ions
+  auto qq = std::unique_ptr<double[]>(new double[salt_charge_ratio + 1]);
+  // temporary mask array
+  auto mask_tmp = std::unique_ptr<int[]>(new int[salt_charge_ratio + 1]);
 
   if (salt_charge[0] <= -salt_charge[1]) {
     // delete one anion and (salt_charge_ratio) cations