diff --git a/src/KSPACE/fix_tune_kspace.cpp b/src/KSPACE/fix_tune_kspace.cpp
index 2dbed26941..5ce867778d 100644
--- a/src/KSPACE/fix_tune_kspace.cpp
+++ b/src/KSPACE/fix_tune_kspace.cpp
@@ -63,6 +63,7 @@ FixTuneKspace::FixTuneKspace(LAMMPS *lmp, int narg, char **arg) :
   // parse arguments
 
   nevery = force->inumeric(FLERR,arg[3]);
+  if (nevery <= 0) error->all(FLERR,"Illegal fix tune/kspace command");
 
   // set up reneighboring
 
diff --git a/src/MC/fix_atom_swap.cpp b/src/MC/fix_atom_swap.cpp
index 7cdee69c39..689aa0a168 100644
--- a/src/MC/fix_atom_swap.cpp
+++ b/src/MC/fix_atom_swap.cpp
@@ -79,6 +79,7 @@ FixAtomSwap::FixAtomSwap(LAMMPS *lmp, int narg, char **arg) :
   double temperature = force->numeric(FLERR,arg[6]);
   beta = 1.0/(force->boltz*temperature);
 
+  if (nevery <= 0) error->all(FLERR,"Illegal fix atom/swap command");
   if (ncycles < 0) error->all(FLERR,"Illegal fix atom/swap command");
   if (seed <= 0) error->all(FLERR,"Illegal fix atom/swap command");
 
diff --git a/src/MC/fix_gcmc.cpp b/src/MC/fix_gcmc.cpp
index 849783ae5e..2fb0015f7b 100644
--- a/src/MC/fix_gcmc.cpp
+++ b/src/MC/fix_gcmc.cpp
@@ -85,6 +85,7 @@ FixGCMC::FixGCMC(LAMMPS *lmp, int narg, char **arg) :
   chemical_potential = force->numeric(FLERR,arg[9]);
   displace = force->numeric(FLERR,arg[10]);
 
+  if (nevery <= 0) error->all(FLERR,"Illegal fix gcmc command");
   if (nexchanges < 0) error->all(FLERR,"Illegal fix gcmc command");
   if (nmcmoves < 0) error->all(FLERR,"Illegal fix gcmc command");
   if (seed <= 0) error->all(FLERR,"Illegal fix gcmc command");
diff --git a/src/QEQ/fix_qeq.cpp b/src/QEQ/fix_qeq.cpp
index d33c841b56..bc044ebae4 100644
--- a/src/QEQ/fix_qeq.cpp
+++ b/src/QEQ/fix_qeq.cpp
@@ -55,6 +55,10 @@ FixQEq::FixQEq(LAMMPS *lmp, int narg, char **arg) :
   tolerance = force->numeric(FLERR,arg[5]);
   maxiter = force->inumeric(FLERR,arg[6]);
 
+  // check for sane arguments
+  if ((nevery <= 0) || (cutoff <= 0.0) || (tolerance <= 0.0) || (maxiter <= 0))
+    error->all(FLERR,"Illegal fix qeq command");
+
   alpha = 0.20;
   swa = 0.0;
   swb = cutoff;
diff --git a/src/REPLICA/neb.cpp b/src/REPLICA/neb.cpp
index 68d2af8bd9..1521598812 100644
--- a/src/REPLICA/neb.cpp
+++ b/src/REPLICA/neb.cpp
@@ -122,7 +122,7 @@ void NEB::command(int narg, char **arg)
 
   if (etol < 0.0) error->all(FLERR,"Illegal NEB command");
   if (ftol < 0.0) error->all(FLERR,"Illegal NEB command");
-  if (nevery == 0) error->universe_all(FLERR,"Illegal NEB command");
+  if (nevery <= 0) error->universe_all(FLERR,"Illegal NEB command");
   if (n1steps % nevery || n2steps % nevery)
     error->universe_all(FLERR,"Illegal NEB command");
 
diff --git a/src/REPLICA/temper.cpp b/src/REPLICA/temper.cpp
index 5b6c310911..ebc26d6061 100644
--- a/src/REPLICA/temper.cpp
+++ b/src/REPLICA/temper.cpp
@@ -87,7 +87,7 @@ void Temper::command(int narg, char **arg)
 
   // swap frequency must evenly divide total # of timesteps
 
-  if (nevery == 0)
+  if (nevery <= 0)
     error->universe_all(FLERR,"Invalid frequency in temper command");
   nswaps = nsteps/nevery;
   if (nswaps*nevery != nsteps)
diff --git a/src/USER-REAXC/fix_qeq_reax.cpp b/src/USER-REAXC/fix_qeq_reax.cpp
index bb0fe3e6d7..0dbb864fb7 100644
--- a/src/USER-REAXC/fix_qeq_reax.cpp
+++ b/src/USER-REAXC/fix_qeq_reax.cpp
@@ -71,6 +71,8 @@ FixQEqReax::FixQEqReax(LAMMPS *lmp, int narg, char **arg) :
   if (narg != 8) error->all(FLERR,"Illegal fix qeq/reax command");
 
   nevery = force->inumeric(FLERR,arg[3]);
+  if (nevery <= 0) error->all(FLERR,"Illegal fix qeq/reax command");
+
   swa = force->numeric(FLERR,arg[4]);
   swb = force->numeric(FLERR,arg[5]);
   tolerance = force->numeric(FLERR,arg[6]);
diff --git a/src/dump_custom.cpp b/src/dump_custom.cpp
index cecaa9b3f8..68097e543d 100644
--- a/src/dump_custom.cpp
+++ b/src/dump_custom.cpp
@@ -60,6 +60,7 @@ DumpCustom::DumpCustom(LAMMPS *lmp, int narg, char **arg) :
   clearstep = 1;
 
   nevery = force->inumeric(FLERR,arg[3]);
+  if (nevery <= 0) error->all(FLERR,"Illegal dump custom command");
 
   // size_one may be shrunk below if additional optional args exist
 
diff --git a/src/dump_local.cpp b/src/dump_local.cpp
index eb08a912fc..e290accede 100644
--- a/src/dump_local.cpp
+++ b/src/dump_local.cpp
@@ -43,6 +43,8 @@ DumpLocal::DumpLocal(LAMMPS *lmp, int narg, char **arg) :
   clearstep = 1;
 
   nevery = force->inumeric(FLERR,arg[3]);
+  if (nevery <= 0) error->all(FLERR,"Illegal dump local command");
+
 
   size_one = nfield = narg-5;
   pack_choice = new FnPtrPack[nfield];