diff --git a/src/MISC/fix_ipi.cpp b/src/MISC/fix_ipi.cpp
index b56c5eebcb..b82339713e 100644
--- a/src/MISC/fix_ipi.cpp
+++ b/src/MISC/fix_ipi.cpp
@@ -200,22 +200,10 @@ FixIPI::FixIPI(LAMMPS *lmp, int narg, char **arg) :
   hasdata = bsize = 0;
 
   // creates a temperature compute for all atoms
-  char** newarg = new char*[3];
-  newarg[0] = (char *) "IPI_TEMP";
-  newarg[1] = (char *) "all";
-  newarg[2] = (char *) "temp";
-  modify->add_compute(3,newarg);
-  delete [] newarg;
+  modify->add_compute("IPI_TEMP all temp");
 
   // creates a  pressure compute to extract the virial
-  newarg = new char*[5];
-  newarg[0] = (char *) "IPI_PRESS";
-  newarg[1] = (char *) "all";
-  newarg[2] = (char *) "pressure";
-  newarg[3] = (char *) "IPI_TEMP";
-  newarg[4] = (char *) "virial";
-  modify->add_compute(5,newarg);
-  delete [] newarg;
+  modify->add_compute("IPI_PRESS all pressure IPI_TEMP virial");
 
   // create instance of Irregular class
   irregular = new Irregular(lmp);
diff --git a/src/PLUMED/fix_plumed.cpp b/src/PLUMED/fix_plumed.cpp
index b38e745b7a..7a142b57f8 100644
--- a/src/PLUMED/fix_plumed.cpp
+++ b/src/PLUMED/fix_plumed.cpp
@@ -215,31 +215,13 @@ FixPlumed::FixPlumed(LAMMPS *lmp, int narg, char **arg) :
 
   // Define compute to calculate potential energy
 
-  id_pe = new char[8];
-  strcpy(id_pe,"plmd_pe");
-  char **newarg = new char*[3];
-  newarg[0] = id_pe;
-  newarg[1] = (char *) "all";
-  newarg[2] = (char *) "pe";
-  modify->add_compute(3,newarg);
-  delete [] newarg;
-  int ipe = modify->find_compute(id_pe);
-  c_pe = modify->compute[ipe];
+  id_pe = utils::strdup("plmd_pe");
+  c_pe = modify->add_compute(std::string(id_pe) + " all pe");
 
   // Define compute to calculate pressure tensor
 
-  id_press = new char[11];
-  strcpy(id_press,"plmd_press");
-  newarg = new char*[5];
-  newarg[0] = id_press;
-  newarg[1] = (char *) "all";
-  newarg[2] = (char *) "pressure";
-  newarg[3] = (char *) "NULL";
-  newarg[4] = (char *) "virial";
-  modify->add_compute(5,newarg);
-  delete [] newarg;
-  int ipress = modify->find_compute(id_press);
-  c_press = modify->compute[ipress];
+  id_press = utils::strdup("plmd_press");
+  c_press = modify->add_compute(std::string(id_press) + " all pressure NULL virial");
 
   for (int i = 0; i < modify->nfix; i++) {
     const char * const check_style = modify->fix[i]->style;