diff --git a/src/DPD-REACT/npair_half_bin_newton_ssa.cpp b/src/DPD-REACT/npair_half_bin_newton_ssa.cpp
index 7393e54f78..902921bc90 100644
--- a/src/DPD-REACT/npair_half_bin_newton_ssa.cpp
+++ b/src/DPD-REACT/npair_half_bin_newton_ssa.cpp
@@ -203,10 +203,9 @@ void NPairHalfBinNewtonSSA::build(NeighList *list)
               if (molecular != Atom::ATOMIC) {
                 if (!moltemplate)
                   which = find_special(special[i],nspecial[i],tag[j]);
-                else if (imol >= 0)
+                else if ((imol >= 0) && onemols[imol]->special)
                   which = find_special(onemols[imol]->special[iatom],
-                                       onemols[imol]->nspecial[iatom],
-                                       tag[j]-tagprev);
+                                       onemols[imol]->nspecial[iatom], tag[j] - tagprev);
                 else which = 0;
                 if (which == 0) neighptr[n++] = j;
                 else if (domain->minimum_image_check(delx,dely,delz))
@@ -286,11 +285,11 @@ void NPairHalfBinNewtonSSA::build(NeighList *list)
                 which = find_special(special[j],nspecial[j],tag[i]);
               else {
                 int jmol = molindex[j];
-                if (jmol >= 0) {
+                if ((jmol >= 0) && onemols[jmol]->special) {
                   int jatom = molatom[j];
                   which = find_special(onemols[jmol]->special[jatom],
-                                     onemols[jmol]->nspecial[jatom],
-                                     tag[i] - (tag[j] - jatom - 1));
+                                       onemols[jmol]->nspecial[jatom],
+                                       tag[i] - (tag[j] - jatom - 1));
                 } else which = 0;
               }
               if (which == 0) neighptr[n++] = j;
diff --git a/src/OPENMP/npair_bin_ghost_omp.cpp b/src/OPENMP/npair_bin_ghost_omp.cpp
index 93dd7b1110..f33bd821f7 100644
--- a/src/OPENMP/npair_bin_ghost_omp.cpp
+++ b/src/OPENMP/npair_bin_ghost_omp.cpp
@@ -135,7 +135,7 @@ void NPairBinGhostOmp<HALF>::build(NeighList *list)
             if (molecular != Atom::ATOMIC) {
               if (!moltemplate)
                 which = find_special(special[i], nspecial[i], tag[j]);
-              else if (imol >= 0)
+              else if ((imol >= 0) && onemols[imol]->special)
                 which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
                                      tag[j] - tagprev);
               else
diff --git a/src/OPENMP/npair_bin_omp.cpp b/src/OPENMP/npair_bin_omp.cpp
index 7922d76612..21bb887177 100644
--- a/src/OPENMP/npair_bin_omp.cpp
+++ b/src/OPENMP/npair_bin_omp.cpp
@@ -207,9 +207,9 @@ void NPairBinOmp<HALF, NEWTON, TRI, SIZE, ATOMONLY>::build(NeighList *list)
               if (molecular != Atom::ATOMIC) {
                 if (!moltemplate)
                   which = find_special(special[i], nspecial[i], tag[j]);
-                else if (imol >= 0)
-                  which = find_special(onemols[imol]->special[iatom], onemols[imol]  ->nspecial[iatom],
-                                       tag[j] - tagprev);
+                else if ((imol >= 0) && onemols[imol]->special)
+                  which = find_special(onemols[imol]->special[iatom],
+                                       onemols[imol]  ->nspecial[iatom], tag[j] - tagprev);
                 else
                   which = 0;
                 if (which == 0)
@@ -230,9 +230,9 @@ void NPairBinOmp<HALF, NEWTON, TRI, SIZE, ATOMONLY>::build(NeighList *list)
               if (molecular != Atom::ATOMIC) {
                 if (!moltemplate)
                   which = find_special(special[i], nspecial[i], tag[j]);
-                else if (imol >= 0)
-                  which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
-                                       tag[j] - tagprev);
+                else if ((imol >= 0) && onemols[imol]->special)
+                  which = find_special(onemols[imol]->special[iatom],
+                                       onemols[imol]->nspecial[iatom], tag[j] - tagprev);
                 else which = 0;
                 if (which == 0)
                   neighptr[n++] = j;
diff --git a/src/OPENMP/npair_multi_old_omp.cpp b/src/OPENMP/npair_multi_old_omp.cpp
index fa790e177a..d07240cf9b 100644
--- a/src/OPENMP/npair_multi_old_omp.cpp
+++ b/src/OPENMP/npair_multi_old_omp.cpp
@@ -204,7 +204,7 @@ void NPairMultiOldOmp<HALF, NEWTON, TRI, SIZE>::build(NeighList *list)
             if (molecular != Atom::ATOMIC) {
               if (!moltemplate)
                 which = find_special(special[i], nspecial[i], tag[j]);
-              else if (imol >= 0)
+              else if ((imol >= 0) && onemols[imol]->special)
                 which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
                                      tag[j] - tagprev);
               else
@@ -223,7 +223,7 @@ void NPairMultiOldOmp<HALF, NEWTON, TRI, SIZE>::build(NeighList *list)
             if (molecular != Atom::ATOMIC) {
               if (!moltemplate)
                 which = find_special(special[i], nspecial[i], tag[j]);
-              else if (imol >= 0)
+              else if ((imol >= 0) && onemols[imol]->special)
                 which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
                                      tag[j] - tagprev);
               else
diff --git a/src/OPENMP/npair_multi_omp.cpp b/src/OPENMP/npair_multi_omp.cpp
index cbc21ebc29..c85726f4fb 100644
--- a/src/OPENMP/npair_multi_omp.cpp
+++ b/src/OPENMP/npair_multi_omp.cpp
@@ -232,9 +232,9 @@ void NPairMultiOmp<HALF, NEWTON, TRI, SIZE, ATOMONLY>::build(NeighList *list)
                 if (molecular != Atom::ATOMIC) {
                   if (!moltemplate)
                     which = find_special(special[i], nspecial[i], tag[j]);
-                  else if (imol >= 0)
-                    which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
-                                         tag[j] - tagprev);
+                  else if ((imol >= 0) && onemols[imol]->special)
+                    which = find_special(onemols[imol]->special[iatom],
+                                         onemols[imol]->nspecial[iatom], tag[j] - tagprev);
                   else
                     which = 0;
                   if (which == 0)
@@ -255,9 +255,9 @@ void NPairMultiOmp<HALF, NEWTON, TRI, SIZE, ATOMONLY>::build(NeighList *list)
                 if (molecular != Atom::ATOMIC) {
                   if (!moltemplate)
                     which = find_special(special[i], nspecial[i], tag[j]);
-                  else if (imol >= 0)
-                    which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
-                                         tag[j] - tagprev);
+                  else if ((imol >= 0) && onemols[imol]->special)
+                    which = find_special(onemols[imol]->special[iatom],
+                                         onemols[imol]->nspecial[iatom], tag[j] - tagprev);
                   else
                     which = 0;
                   if (which == 0)
diff --git a/src/OPENMP/npair_nsq_ghost_omp.cpp b/src/OPENMP/npair_nsq_ghost_omp.cpp
index a270fbb84d..59fa8ed6f5 100644
--- a/src/OPENMP/npair_nsq_ghost_omp.cpp
+++ b/src/OPENMP/npair_nsq_ghost_omp.cpp
@@ -131,7 +131,7 @@ void NPairNsqGhostOmp<HALF>::build(NeighList *list)
           if (molecular != Atom::ATOMIC) {
             if (!moltemplate)
               which = find_special(special[i], nspecial[i], tag[j]);
-            else if (imol >= 0)
+            else if ((imol >= 0) && onemols[imol]->special)
               which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
                                    tag[j] - tagprev);
             else
diff --git a/src/OPENMP/npair_nsq_omp.cpp b/src/OPENMP/npair_nsq_omp.cpp
index 5d6aa518b0..1a7058791c 100644
--- a/src/OPENMP/npair_nsq_omp.cpp
+++ b/src/OPENMP/npair_nsq_omp.cpp
@@ -181,7 +181,7 @@ void NPairNsqOmp<HALF, NEWTON, TRI, SIZE>::build(NeighList *list)
           if (molecular != Atom::ATOMIC) {
             if (!moltemplate)
               which = find_special(special[i], nspecial[i], tag[j]);
-            else if (imol >= 0)
+            else if ((imol >= 0) && onemols[imol]->special)
               which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
                                    tag[j] - tagprev);
             else
@@ -200,7 +200,7 @@ void NPairNsqOmp<HALF, NEWTON, TRI, SIZE>::build(NeighList *list)
           if (molecular != Atom::ATOMIC) {
             if (!moltemplate)
               which = find_special(special[i], nspecial[i], tag[j]);
-            else if (imol >= 0)
+            else if ((imol >= 0) && onemols[imol]->special)
               which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
                                    tag[j] - tagprev);
             else
diff --git a/src/OPENMP/npair_respa_bin_omp.cpp b/src/OPENMP/npair_respa_bin_omp.cpp
index a069affb06..691d807498 100644
--- a/src/OPENMP/npair_respa_bin_omp.cpp
+++ b/src/OPENMP/npair_respa_bin_omp.cpp
@@ -204,7 +204,7 @@ void NPairRespaBinOmp<NEWTON, TRI>::build(NeighList *list)
           if (molecular != Atom::ATOMIC) {
             if (!moltemplate)
               which = find_special(special[i], nspecial[i], tag[j]);
-            else if (imol >= 0)
+            else if ((imol >= 0) && onemols[imol]->special)
               which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
                                    tag[j] - tagprev);
             else
diff --git a/src/OPENMP/npair_respa_nsq_omp.cpp b/src/OPENMP/npair_respa_nsq_omp.cpp
index deba473678..8483872ca0 100644
--- a/src/OPENMP/npair_respa_nsq_omp.cpp
+++ b/src/OPENMP/npair_respa_nsq_omp.cpp
@@ -186,7 +186,7 @@ void NPairRespaNsqOmp<NEWTON, TRI>::build(NeighList *list)
         if (molecular != Atom::ATOMIC) {
           if (!moltemplate)
             which = find_special(special[i], nspecial[i], tag[j]);
-          else if (imol >= 0)
+          else if ((imol >= 0) && onemols[imol]->special)
             which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
                                  tag[j] - tagprev);
           else
diff --git a/src/npair_bin.cpp b/src/npair_bin.cpp
index 2c6fbbb49b..3ed567a008 100644
--- a/src/npair_bin.cpp
+++ b/src/npair_bin.cpp
@@ -199,9 +199,9 @@ void NPairBin<HALF, NEWTON, TRI, SIZE, ATOMONLY>::build(NeighList *list)
               if (molecular != Atom::ATOMIC) {
                 if (!moltemplate)
                   which = find_special(special[i], nspecial[i], tag[j]);
-                else if (imol >= 0)
-                  which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
-                                       tag[j] - tagprev);
+                else if ((imol >= 0) && onemols[imol]->special)
+                  which = find_special(onemols[imol]->special[iatom],
+                                       onemols[imol]->nspecial[iatom], tag[j] - tagprev);
                 else
                   which = 0;
                 if (which == 0)
@@ -222,9 +222,9 @@ void NPairBin<HALF, NEWTON, TRI, SIZE, ATOMONLY>::build(NeighList *list)
               if (molecular != Atom::ATOMIC) {
                 if (!moltemplate)
                   which = find_special(special[i], nspecial[i], tag[j]);
-                else if (imol >= 0)
-                  which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
-                                       tag[j] - tagprev);
+                else if ((imol >= 0) && onemols[imol]->special)
+                  which = find_special(onemols[imol]->special[iatom],
+                                       onemols[imol]->nspecial[iatom], tag[j] - tagprev);
                 else
                   which = 0;
                 if (which == 0)
diff --git a/src/npair_bin_ghost.cpp b/src/npair_bin_ghost.cpp
index 8403bc8f3d..5efe7898bb 100644
--- a/src/npair_bin_ghost.cpp
+++ b/src/npair_bin_ghost.cpp
@@ -130,9 +130,9 @@ void NPairBinGhost<HALF>::build(NeighList *list)
             if (molecular != Atom::ATOMIC) {
               if (!moltemplate)
                 which = find_special(special[i], nspecial[i], tag[j]);
-              else if (imol >= 0)
-                which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
-                                     tag[j] - tagprev);
+              else if ((imol >= 0) && onemols[imol]->special)
+                which = find_special(onemols[imol]->special[iatom],
+                                     onemols[imol]->nspecial[iatom], tag[j] - tagprev);
               else
                 which = 0;
               if (which == 0)
diff --git a/src/npair_multi.cpp b/src/npair_multi.cpp
index 44c68a9195..f41088d324 100644
--- a/src/npair_multi.cpp
+++ b/src/npair_multi.cpp
@@ -229,9 +229,9 @@ void NPairMulti<HALF, NEWTON, TRI, SIZE, ATOMONLY>::build(NeighList *list)
                 if (molecular != Atom::ATOMIC) {
                   if (!moltemplate)
                     which = find_special(special[i], nspecial[i], tag[j]);
-                  else if (imol >= 0)
-                    which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
-                                         tag[j] - tagprev);
+                  else if ((imol >= 0) && onemols[imol]->special)
+                    which = find_special(onemols[imol]->special[iatom],
+                                         onemols[imol]->nspecial[iatom], tag[j] - tagprev);
                   else
                     which = 0;
                   if (which == 0)
@@ -252,9 +252,9 @@ void NPairMulti<HALF, NEWTON, TRI, SIZE, ATOMONLY>::build(NeighList *list)
                 if (molecular != Atom::ATOMIC) {
                   if (!moltemplate)
                     which = find_special(special[i], nspecial[i], tag[j]);
-                  else if (imol >= 0)
-                    which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
-                                         tag[j] - tagprev);
+                  else if ((imol >= 0) && onemols[imol]->special)
+                    which = find_special(onemols[imol]->special[iatom],
+                                         onemols[imol]->nspecial[iatom], tag[j] - tagprev);
                   else
                     which = 0;
                   if (which == 0)
diff --git a/src/npair_multi_old.cpp b/src/npair_multi_old.cpp
index 3d983bd7fd..8d2bb71f10 100644
--- a/src/npair_multi_old.cpp
+++ b/src/npair_multi_old.cpp
@@ -197,7 +197,7 @@ void NPairMultiOld<HALF, NEWTON, TRI, SIZE>::build(NeighList *list)
             if (molecular != Atom::ATOMIC) {
               if (!moltemplate)
                 which = find_special(special[i], nspecial[i], tag[j]);
-              else if (imol >= 0)
+              else if ((imol >= 0) && onemols[imol]->special)
                 which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
                                      tag[j] - tagprev);
               else
@@ -216,7 +216,7 @@ void NPairMultiOld<HALF, NEWTON, TRI, SIZE>::build(NeighList *list)
             if (molecular != Atom::ATOMIC) {
               if (!moltemplate)
                 which = find_special(special[i], nspecial[i], tag[j]);
-              else if (imol >= 0)
+              else if ((imol >= 0) && onemols[imol]->special)
                 which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
                                      tag[j] - tagprev);
               else
diff --git a/src/npair_nsq.cpp b/src/npair_nsq.cpp
index 9f469de480..ec64e7d2a3 100644
--- a/src/npair_nsq.cpp
+++ b/src/npair_nsq.cpp
@@ -173,7 +173,7 @@ void NPairNsq<HALF, NEWTON, TRI, SIZE>::build(NeighList *list)
           if (molecular != Atom::ATOMIC) {
             if (!moltemplate)
               which = find_special(special[i], nspecial[i], tag[j]);
-            else if (imol >= 0)
+            else if ((imol >= 0) && onemols[imol]->special)
               which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
                                    tag[j] - tagprev);
             else
@@ -192,7 +192,7 @@ void NPairNsq<HALF, NEWTON, TRI, SIZE>::build(NeighList *list)
           if (molecular != Atom::ATOMIC) {
             if (!moltemplate)
               which = find_special(special[i], nspecial[i], tag[j]);
-            else if (imol >= 0)
+            else if ((imol >= 0) && onemols[imol]->special)
               which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
                                    tag[j] - tagprev);
             else
diff --git a/src/npair_nsq_ghost.cpp b/src/npair_nsq_ghost.cpp
index 47009deff7..2f9c5123b7 100644
--- a/src/npair_nsq_ghost.cpp
+++ b/src/npair_nsq_ghost.cpp
@@ -127,10 +127,9 @@ void NPairNsqGhost<HALF>::build(NeighList *list)
           if (molecular != Atom::ATOMIC) {
             if (!moltemplate)
               which = find_special(special[i],nspecial[i],tag[j]);
-            else if (imol >= 0)
-              which = find_special(onemols[imol]->special[iatom],
-                                   onemols[imol]->nspecial[iatom],
-                                   tag[j]-tagprev);
+            else if ((imol >= 0) && onemols[imol]->special)
+              which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
+                                   tag[j] - tagprev);
             else which = 0;
             if (which == 0) neighptr[n++] = j;
             else if (domain->minimum_image_check(delx,dely,delz))
diff --git a/src/npair_respa_bin.cpp b/src/npair_respa_bin.cpp
index 5347f4d3a0..6a6c52de87 100644
--- a/src/npair_respa_bin.cpp
+++ b/src/npair_respa_bin.cpp
@@ -192,7 +192,7 @@ void NPairRespaBin<NEWTON, TRI>::build(NeighList *list)
           if (molecular != Atom::ATOMIC) {
             if (!moltemplate)
               which = find_special(special[i], nspecial[i], tag[j]);
-            else if (imol >= 0)
+            else if ((imol >= 0) && onemols[imol]->special)
               which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
                                    tag[j] - tagprev);
             else
diff --git a/src/npair_respa_nsq.cpp b/src/npair_respa_nsq.cpp
index 065c9eb6d6..43bf0d649c 100644
--- a/src/npair_respa_nsq.cpp
+++ b/src/npair_respa_nsq.cpp
@@ -179,7 +179,7 @@ void NPairRespaNsq<NEWTON, TRI>::build(NeighList *list)
         if (molecular != Atom::ATOMIC) {
           if (!moltemplate)
             which = find_special(special[i], nspecial[i], tag[j]);
-          else if (imol >= 0)
+          else if ((imol >= 0) && onemols[imol]->special)
             which = find_special(onemols[imol]->special[iatom], onemols[imol]->nspecial[iatom],
                                  tag[j] - tagprev);
           else