diff --git a/src/neighbor.cpp b/src/neighbor.cpp
index 4ab1c80b7b..f0013714ea 100644
--- a/src/neighbor.cpp
+++ b/src/neighbor.cpp
@@ -69,6 +69,7 @@ Neighbor::Neighbor(LAMMPS *lmp) : Pointers(lmp)
   dist_check = 1;
   pgsize = 100000;
   oneatom = 2000;
+  binsizeflag = 0;
 
   cutneighsq = NULL;
   cuttype = NULL;
@@ -1088,7 +1089,8 @@ void Neighbor::setup_bins()
   // special case of all cutoffs = 0.0, binsize = box size
 
   double binsize_optimal;
-  if (style == BIN) binsize_optimal = 0.5*cutneighmax;
+  if (binsizeflag) binsize_optimal = binsize_user;
+  else if (style == BIN) binsize_optimal = 0.5*cutneighmax;
   else binsize_optimal = 0.5*cutneighmin;
   if (binsize_optimal == 0.0) binsize_optimal = bbox[0];
   double binsizeinv = 1.0/binsize_optimal;
@@ -1280,6 +1282,12 @@ void Neighbor::modify_params(int narg, char **arg)
       if (iarg+2 > narg) error->all("Illegal neigh_modify command");
       oneatom = atoi(arg[iarg+1]);
       iarg += 2;
+    } else if (strcmp(arg[iarg],"binsize") == 0) {
+      if (iarg+2 > narg) error->all("Illegal neigh_modify command");
+      binsize_user = atof(arg[iarg+1]);
+      if (binsize_user <= 0.0) binsizeflag = 0;
+      else binsizeflag = 1;
+      iarg += 2;
     } else if (strcmp(arg[iarg],"exclude") == 0) {
       if (iarg+2 > narg) error->all("Illegal neigh_modify command");
 
diff --git a/src/neighbor.h b/src/neighbor.h
index e48e326352..39f5788986 100644
--- a/src/neighbor.h
+++ b/src/neighbor.h
@@ -102,7 +102,10 @@ class Neighbor : protected Pointers {
   int mbinx,mbiny,mbinz;
   int mbinxlo,mbinylo,mbinzlo;
 
-  double binsizex,binsizey,binsizez;  // bin sizes and inverse sizes
+  int binsizeflag;                 // user-chosen bin size
+  double binsize_user;
+
+  double binsizex,binsizey,binsizez;  // actual bin sizes and inverse sizes
   double bininvx,bininvy,bininvz;
 
   int sx,sy,sz,smax;               // bin stencil extents