diff --git a/src/comm.cpp b/src/comm.cpp
index 02999fd541..1b1546f893 100644
--- a/src/comm.cpp
+++ b/src/comm.cpp
@@ -75,6 +75,7 @@ Comm::Comm(LAMMPS *lmp) : Pointers(lmp)
   maxexchange = maxexchange_atom = maxexchange_fix = 0;
   maxexchange_fix_dynamic = 0;
   bufextra = BUFEXTRA;
+  bufextra_max = bufextra;
 
   grid2proc = nullptr;
   xsplit = ysplit = zsplit = nullptr;
diff --git a/src/comm.h b/src/comm.h
index fde4c3b81f..8515866dff 100644
--- a/src/comm.h
+++ b/src/comm.h
@@ -140,6 +140,7 @@ class Comm : protected Pointers {
   int maxexchange_fix;            // static contribution to maxexchange from Fixes
   int maxexchange_fix_dynamic;    // 1 if a fix has a dynamic contribution
   int bufextra;                   // augment send buf size for an exchange atom
+  int bufextra_max;
 
   int gridflag;        // option for creating 3d grid
   int mapflag;         // option for mapping procs to 3d grid
diff --git a/src/comm_brick.cpp b/src/comm_brick.cpp
index cf38271029..c75b183584 100644
--- a/src/comm_brick.cpp
+++ b/src/comm_brick.cpp
@@ -133,9 +133,11 @@ void CommBrick::init()
 {
   Comm::init();
 
-  int bufextra_old = bufextra;
   init_exchange();
-  if (bufextra > bufextra_old) grow_send(maxsend+bufextra,2);
+  if (bufextra > bufextra_max) {
+    grow_send(maxsend+bufextra,2);
+    bufextra_max = bufextra;
+  }
 
   // memory for multi style communication
   // allocate in setup
@@ -672,9 +674,11 @@ void CommBrick::exchange()
   // only need to reset if a fix can dynamically add to size of single atom
 
   if (maxexchange_fix_dynamic) {
-    int bufextra_old = bufextra;
     init_exchange();
-    if (bufextra > bufextra_old) grow_send(maxsend+bufextra,2);
+    if (bufextra > bufextra_max) {
+      grow_send(maxsend+bufextra,2);
+      bufextra_max = bufextra;
+    }
   }
 
   // subbox bounds for orthogonal or triclinic
diff --git a/src/comm_tiled.cpp b/src/comm_tiled.cpp
index b864e0523d..f4657c4790 100644
--- a/src/comm_tiled.cpp
+++ b/src/comm_tiled.cpp
@@ -943,9 +943,11 @@ void CommTiled::exchange()
   // only need to reset if a fix can dynamically add to size of single atom
 
   if (maxexchange_fix_dynamic) {
-    int bufextra_old = bufextra;
     init_exchange();
-    if (bufextra > bufextra_old) grow_send(maxsend+bufextra,2);
+    if (bufextra > bufextra_max) {
+      grow_send(maxsend+bufextra,2);
+      bufextra = bufextra_max;
+    }
   }
 
   // domain properties used in exchange method and methods it calls