diff --git a/src/balance.h b/src/balance.h
index 2e3f003fbd..df8ac307b4 100644
--- a/src/balance.h
+++ b/src/balance.h
@@ -45,6 +45,7 @@ class Balance : public Command {
   int *bisection(int sortflag = 0);
   void dumpout(bigint);
 
+  static constexpr int BSTR_SIZE = 3;
  private:
   int me, nprocs;
 
@@ -56,7 +57,6 @@ class Balance : public Command {
 
   int nitermax;    // params for shift LB
   double stopthresh;
-  static constexpr int BSTR_SIZE = 3;
   char bstr[BSTR_SIZE+1];
 
   int shift_allocate;       // 1 if SHIFT vectors have been allocated
diff --git a/src/fix_balance.cpp b/src/fix_balance.cpp
index 40fa7255f6..2c76f13bf0 100644
--- a/src/fix_balance.cpp
+++ b/src/fix_balance.cpp
@@ -64,14 +64,15 @@ FixBalance::FixBalance(LAMMPS *lmp, int narg, char **arg) :
   int iarg = 5;
   if (lbstyle == SHIFT) {
     if (iarg+4 > narg) error->all(FLERR,"Illegal fix balance command");
-    if (strlen(arg[iarg+1]) > 3)
+    if (strlen(arg[iarg+1]) > Balance::BSTR_SIZE)
       error->all(FLERR,"Illegal fix balance command");
-    strcpy(bstr,arg[iarg+1]);
+    strncpy(bstr,arg[iarg+1], Balance::BSTR_SIZE+1);
     nitermax = utils::inumeric(FLERR,arg[iarg+2],false,lmp);
     if (nitermax <= 0) error->all(FLERR,"Illegal fix balance command");
     stopthresh = utils::numeric(FLERR,arg[iarg+3],false,lmp);
     if (stopthresh < 1.0) error->all(FLERR,"Illegal fix balance command");
     iarg += 4;
+
   } else if (lbstyle == BISECTION) {
     iarg++;
   }