diff --git a/src/GRANULAR/pair_gran_hooke_history.cpp b/src/GRANULAR/pair_gran_hooke_history.cpp
index f212bdf97a..c9cdba1e35 100644
--- a/src/GRANULAR/pair_gran_hooke_history.cpp
+++ b/src/GRANULAR/pair_gran_hooke_history.cpp
@@ -481,12 +481,12 @@ void PairGranHookeHistory::init_style()
   int itype;
   for (i = 1; i <= atom->ntypes; i++) {
     onerad_dynamic[i] = onerad_frozen[i] = 0.0;
-    for (auto ipour : pours) {
+    for (auto &ipour : pours) {
       itype = i;
       double maxrad = *((double *) ipour->extract("radius", itype));
       if (maxrad > 0.0) onerad_dynamic[i] = maxrad;
     }
-    for (auto idep : deps) {
+    for (auto &idep : deps) {
       itype = i;
       double maxrad = *((double *) idep->extract("radius", itype));
       if (maxrad > 0.0) onerad_dynamic[i] = maxrad;
diff --git a/src/GRANULAR/pair_granular.cpp b/src/GRANULAR/pair_granular.cpp
index fc18d3f521..8bcfc723ac 100644
--- a/src/GRANULAR/pair_granular.cpp
+++ b/src/GRANULAR/pair_granular.cpp
@@ -1160,12 +1160,12 @@ void PairGranular::init_style()
   int itype;
   for (i = 1; i <= atom->ntypes; i++) {
     onerad_dynamic[i] = onerad_frozen[i] = 0.0;
-    for (auto ipour : pours) {
+    for (auto &ipour : pours) {
       itype = i;
       double maxrad = *((double *) ipour->extract("radius", itype));
       if (maxrad > 0.0) onerad_dynamic[i] = maxrad;
     }
-    for (auto idep : deps) {
+    for (auto &idep : deps) {
       itype = i;
       double maxrad = *((double *) idep->extract("radius", itype));
       if (maxrad > 0.0) onerad_dynamic[i] = maxrad;
diff --git a/src/comm.cpp b/src/comm.cpp
index c32183ad35..48dae2368a 100644
--- a/src/comm.cpp
+++ b/src/comm.cpp
@@ -202,7 +202,7 @@ void Comm::init()
   if (ghost_velocity) size_border += atom->avec->size_velocity;
 
   const auto &fix_list = modify->get_fix_list();
-  for (auto fix : fix_list)
+  for (const auto &fix : fix_list)
     size_border += fix->comm_border;
 
   // per-atom limits for communication
@@ -218,7 +218,7 @@ void Comm::init()
   if (force->pair) maxforward = MAX(maxforward,force->pair->comm_forward);
   if (force->pair) maxreverse = MAX(maxreverse,force->pair->comm_reverse);
 
-  for (auto fix : fix_list) {
+  for (const auto &fix : fix_list) {
     maxforward = MAX(maxforward,fix->comm_forward);
     maxreverse = MAX(maxreverse,fix->comm_reverse);
   }
@@ -243,7 +243,7 @@ void Comm::init()
   maxexchange_atom = atom->avec->maxexchange;
 
   maxexchange_fix_dynamic = 0;
-  for (auto fix : fix_list)
+  for (const auto &fix : fix_list)
     if (fix->maxexchange_dynamic) maxexchange_fix_dynamic = 1;
 
   if ((mode == Comm::MULTI) && (neighbor->style != Neighbor::MULTI))
@@ -266,7 +266,7 @@ void Comm::init()
 void Comm::init_exchange()
 {
   maxexchange_fix = 0;
-  for (auto fix : modify->get_fix_list())
+  for (const auto &fix : modify->get_fix_list())
     maxexchange_fix += fix->maxexchange;
 
   maxexchange = maxexchange_atom + maxexchange_fix;
diff --git a/src/group.cpp b/src/group.cpp
index cfe0d2cc06..0dc0a560dd 100644
--- a/src/group.cpp
+++ b/src/group.cpp
@@ -105,7 +105,7 @@ void Group::assign(int narg, char **arg)
     int igroup = find(arg[0]);
     if (igroup == -1) error->all(FLERR,"Could not find group delete group ID");
     if (igroup == 0) error->all(FLERR,"Cannot delete group all");
-    for (auto fix : modify->get_fix_list())
+    for (const auto &fix : modify->get_fix_list())
       if (fix->igroup == igroup)
         error->all(FLERR,"Cannot delete group currently used by a fix");
     for (i = 0; i < modify->ncompute; i++)
diff --git a/src/info.cpp b/src/info.cpp
index 8f04e14ae4..4e95a58759 100644
--- a/src/info.cpp
+++ b/src/info.cpp
@@ -569,7 +569,7 @@ void Info::command(int narg, char **arg)
     int i = 0;
     char **names = group->names;
     fputs("\nCompute information:\n",out);
-    for (auto compute : modify->get_compute_list())
+    for (const auto &compute : modify->get_compute_list())
       fmt::print(out,"Compute[{:3d}]:  {:16}  style = {:16}  group = {}\n", i++,
                  std::string(compute->id)+',',std::string(compute->style)+',',
                  names[compute->igroup]);
@@ -598,7 +598,7 @@ void Info::command(int narg, char **arg)
     int i = 0;
     char **names = group->names;
     fputs("\nFix information:\n",out);
-    for (auto fix : modify->get_fix_list())
+    for (const auto &fix : modify->get_fix_list())
       fmt::print(out, "Fix[{:3d}]:      {:16}  style = {:16}  group = {}\n",i++,
                  std::string(fix->id)+',',std::string(fix->style)+',',names[fix->igroup]);
   }
@@ -906,7 +906,7 @@ bool Info::is_defined(const char *category, const char *name)
         return true;
     }
   } else if (strcmp(category,"fix") == 0) {
-    for (auto fix : modify->get_fix_list()) {
+    for (const auto &fix : modify->get_fix_list()) {
       if (strcmp(fix->id,name) == 0)
         return true;
     }
@@ -1011,7 +1011,7 @@ static std::vector<std::string> get_style_names(std::map<std::string, ValueType>
   std::vector<std::string> names;
 
   names.reserve(styles->size());
-  for (auto const& kv : *styles) {
+  for (auto const &kv : *styles) {
     // skip "secret" styles
     if (isupper(kv.first[0])) continue;
     names.push_back(kv.first);
diff --git a/src/verlet.cpp b/src/verlet.cpp
index 0a5a66ebc2..aa180f5644 100644
--- a/src/verlet.cpp
+++ b/src/verlet.cpp
@@ -53,7 +53,7 @@ void Verlet::init()
   // warn if no fixes doing time integration
 
   bool do_time_integrate = false;
-  for (auto fix : modify->get_fix_list())
+  for (const auto &fix : modify->get_fix_list())
     if (fix->time_integrate) do_time_integrate;
 
   if (!do_time_integrate && (comm->me == 0))
diff --git a/src/write_data.cpp b/src/write_data.cpp
index 9684ae6901..c2c59fd046 100644
--- a/src/write_data.cpp
+++ b/src/write_data.cpp
@@ -213,7 +213,7 @@ void WriteData::write(const std::string &file)
   // extra sections managed by fixes
 
   if (fixflag)
-    for (auto ifix : modify->get_fix_list())
+    for (auto &ifix : modify->get_fix_list())
       if (ifix->wd_section)
         for (int m = 0; m < ifix->wd_section; m++) fix(ifix,m);
 
@@ -267,7 +267,7 @@ void WriteData::header()
   // fix info
 
   if (fixflag)
-    for (auto ifix : modify->get_fix_list())
+    for (auto &ifix : modify->get_fix_list())
       if (ifix->wd_header)
         for (int m = 0; m < ifix->wd_header; m++)
           ifix->write_data_header(fp,m);
diff --git a/src/write_restart.cpp b/src/write_restart.cpp
index 5580a564c7..261429c95d 100644
--- a/src/write_restart.cpp
+++ b/src/write_restart.cpp
@@ -413,7 +413,7 @@ void WriteRestart::write(const std::string &file)
 
   // invoke any fixes that write their own restart file
 
-  for (auto fix : modify->get_fix_list())
+  for (auto &fix : modify->get_fix_list())
     if (fix->restart_file)
       fix->write_restart_file(file.c_str());
 }