diff --git a/src/nrncvode/cvodeobj.cpp b/src/nrncvode/cvodeobj.cpp
index 43396a3c63..89b2ca3e58 100644
--- a/src/nrncvode/cvodeobj.cpp
+++ b/src/nrncvode/cvodeobj.cpp
@@ -970,7 +970,7 @@ void Cvode::maxstate(double* pd) {
 
 void Cvode::maxacor(double* pd) {
     if (maxacor_) {
-        for (NrnThread* nt: for_threads(nrn_threads, nrn_nthread)) {
+        for (const NrnThread* nt: for_threads(nrn_threads, nrn_nthread)) {
             double* m = n_vector_data(maxacor_, nt->id);
             int n = ctd_[nt->id].nvsize_;
             int o = ctd_[nt->id].nvoffset_;
diff --git a/src/nrncvode/netcvode.cpp b/src/nrncvode/netcvode.cpp
index ab80d10449..0110299653 100644
--- a/src/nrncvode/netcvode.cpp
+++ b/src/nrncvode/netcvode.cpp
@@ -1460,7 +1460,6 @@ bool NetCvode::init_global() {
     structure_change_cnt_ = structure_change_cnt;
     matrix_change_cnt_ = -1;
     playrec_change_cnt_ = 0;
-    NrnThread* _nt;
     // We copy Memb_list* into cml->ml below. At the moment this CVode code
     // generates its own complicated set of Memb_list* that operate in
     // list-of-handles mode instead of referring to contiguous sets of values.
@@ -3963,7 +3962,6 @@ void NetCvode::re_init(double t) {
 }
 
 void NetCvode::fornetcon_prepare() {
-    NrnThread* nt;
     NrnThreadMembList* tml;
     if (fornetcon_change_cnt_ == structure_change_cnt) {
         return;
diff --git a/src/nrniv/nrncore_write/data/cell_group.cpp b/src/nrniv/nrncore_write/data/cell_group.cpp
index e93f9bfea8..85fb6f8607 100644
--- a/src/nrniv/nrncore_write/data/cell_group.cpp
+++ b/src/nrniv/nrncore_write/data/cell_group.cpp
@@ -552,9 +552,8 @@ void CellGroup::mk_tml_with_art(neuron::model_sorted_token const& cache_token, C
 size_t CellGroup::get_mla_rankbytes(CellGroup* cellgroups_) {
     size_t mla_rankbytes = 0;
     size_t nbytes;
-    NrnThread* nt;
     NrnThreadMembList* tml;
-    for (NrnThread* nt: for_threads(nrn_threads, nrn_nthread)) {
+    for (const NrnThread* nt: for_threads(nrn_threads, nrn_nthread)) {
         size_t threadbytes = 0;
         size_t npnt = 0;
         size_t nart = 0;
diff --git a/src/nrniv/savstate.cpp b/src/nrniv/savstate.cpp
index c3fcd7199f..bc6e9f2b6a 100644
--- a/src/nrniv/savstate.cpp
+++ b/src/nrniv/savstate.cpp
@@ -597,7 +597,7 @@ void SaveState::save() {
     if (!check(false)) {
         alloc();
     }
-    for (NrnThread* nt: for_threads(nrn_threads, nrn_nthread)) {
+    for (const NrnThread* nt: for_threads(nrn_threads, nrn_nthread)) {
         assert(t == nt->_t);
     }
     t_ = t;
@@ -1192,7 +1192,6 @@ void SaveState::free_tq() {
 void SaveState::alloc_tq() {
     free_tq();
     tqcnt_ = 0;
-    NrnThread* nt;
     for (NrnThread* nt: for_threads(nrn_threads, nrn_nthread)) {
         TQueue* tq = net_cvode_instance_event_queue(nt);
         this_savestate = this;
diff --git a/src/nrnoc/multicore.cpp b/src/nrnoc/multicore.cpp
index ffe5bedd1d..7827bce1b3 100644
--- a/src/nrnoc/multicore.cpp
+++ b/src/nrnoc/multicore.cpp
@@ -766,7 +766,7 @@ void reorder_secorder() {
       in either case, we can then point to v, d, rhs in proper
       node order
     */
-    for (NrnThread* _nt: for_threads(nrn_threads, nrn_nthread))
+    for (const NrnThread* _nt: for_threads(nrn_threads, nrn_nthread))
         for (inode = 0; inode < _nt->end; ++inode) {
             _nt->_v_node[inode]->_classical_parent = _nt->_v_parent[inode];
         }
diff --git a/src/nrnoc/treeset.cpp b/src/nrnoc/treeset.cpp
index e4a6466277..e24a45b196 100644
--- a/src/nrnoc/treeset.cpp
+++ b/src/nrnoc/treeset.cpp
@@ -1793,7 +1793,7 @@ int nrn_modeltype(void) {
     type = 0;
     if (nrn_global_ncell > 0) {
         type = 1;
-        for (NrnThread* nt: for_threads(nrn_threads, nrn_nthread))
+        for (const NrnThread* nt: for_threads(nrn_threads, nrn_nthread))
             if (nt->_ecell_memb_list) {
                 type = 2;
             }