diff --git a/src/MANYBODY/pair_tersoff_zbl.h b/src/MANYBODY/pair_tersoff_zbl.h
index c34f94a08d..34bec05195 100755
--- a/src/MANYBODY/pair_tersoff_zbl.h
+++ b/src/MANYBODY/pair_tersoff_zbl.h
@@ -29,7 +29,7 @@ class PairTersoffZBL : public PairTersoff {
   PairTersoffZBL(class LAMMPS *);
   ~PairTersoffZBL() {}
 
- private:
+ protected:
   double global_a_0;                // Bohr radius for Coulomb repulsion
   double global_epsilon_0;        // permittivity of vacuum for Coulomb repulsion
   double global_e;                // proton charge (negative of electron charge)
diff --git a/src/MC/fix_gcmc.cpp b/src/MC/fix_gcmc.cpp
index 2fb0015f7b..3d025e12fd 100644
--- a/src/MC/fix_gcmc.cpp
+++ b/src/MC/fix_gcmc.cpp
@@ -368,7 +368,7 @@ FixGCMC::~FixGCMC()
       delete [] grouptypestrings[igroup];
     memory->sfree(grouptypestrings);
   }
-  if (full_flag) {
+  if (full_flag && group) {
     int igroupall = group->find("all");
     neighbor->exclusion_group_group_delete(exclusion_group,igroupall);
   }
diff --git a/src/compute_chunk_atom.cpp b/src/compute_chunk_atom.cpp
index 5412817d59..e7ca24d29c 100644
--- a/src/compute_chunk_atom.cpp
+++ b/src/compute_chunk_atom.cpp
@@ -441,7 +441,7 @@ ComputeChunkAtom::ComputeChunkAtom(LAMMPS *lmp, int narg, char **arg) :
 
   nmax = 0;
   chunk = NULL;
-  nmaxint = 0;
+  nmaxint = -1;
   ichunk = NULL;
   exclude = NULL;
 
@@ -1989,7 +1989,7 @@ void ComputeChunkAtom::set_arrays(int i)
 
 double ComputeChunkAtom::memory_usage()
 {
-  double bytes = 2*nmaxint * sizeof(int);          // ichunk,exclude
+  double bytes = 2*MAX(nmaxint,0) * sizeof(int);   // ichunk,exclude
   bytes += nmax * sizeof(double);                  // chunk
   bytes += ncoord*nchunk * sizeof(double);         // coord
   if (compress) bytes += nchunk * sizeof(int);     // chunkID