diff --git a/src/REAXFF/fix_reaxff_bonds.cpp b/src/REAXFF/fix_reaxff_bonds.cpp
index 30c55d8f1a..80cd8c7c85 100644
--- a/src/REAXFF/fix_reaxff_bonds.cpp
+++ b/src/REAXFF/fix_reaxff_bonds.cpp
@@ -56,8 +56,8 @@ FixReaxFFBonds::FixReaxFFBonds(LAMMPS *lmp, int narg, char **arg) :
       if (!fp) error->one(FLERR,"Cannot open compressed file");
     } else fp = fopen(arg[4],"w");
 
-    if (!fp) error->one(FLERR,fmt::format("Cannot open fix reaxff/bonds file {}: "
-                                          "{}",arg[4],utils::getsyserror()));
+    if (!fp) error->one(FLERR,fmt::format("Cannot open fix reaxff/bonds file {}: {}",
+                                          arg[4],utils::getsyserror()));
   }
 
   if (atom->tag_consecutive() == 0)
@@ -249,14 +249,12 @@ void FixReaxFFBonds::RecvBuffer(double *buf, int nbuf, int nbuf_local,
   MPI_Request irequest, irequest2;
 
   if (me == 0) {
-    fprintf(fp,"# Timestep " BIGINT_FORMAT " \n",ntimestep);
-    fprintf(fp,"# \n");
-    fprintf(fp,"# Number of particles %d \n",natoms);
-    fprintf(fp,"# \n");
-    fprintf(fp,"# Max number of bonds per atom %d with "
-            "coarse bond order cutoff %5.3f \n",maxnum,cutof3);
-    fprintf(fp,"# Particle connection table and bond orders \n");
-    fprintf(fp,"# id type nb id_1...id_nb mol bo_1...bo_nb abo nlp q \n");
+    fmt::print(fp,"# Timestep {}\n#\n",ntimestep);
+    fmt::print(fp,"# Number of particles {}\n#\n",natoms);
+    fmt::print(fp,"# Max number of bonds per atom {} with coarse bond order cutoff {:5.3f}\n",
+               maxnum,cutof3);
+    fmt::print(fp,"# Particle connection table and bond orders\n"
+               "# id type nb id_1...id_nb mol bo_1...bo_nb abo nlp q\n");
   }
 
   j = 2;
@@ -278,30 +276,26 @@ void FixReaxFFBonds::RecvBuffer(double *buf, int nbuf, int nbuf_local,
         avqtmp = buf[j+3];
         numbonds = nint(buf[j+4]);
 
-        fprintf(fp," " TAGINT_FORMAT " %d %d",itag,itype,numbonds);
-
-        for (k = 5; k < 5+numbonds; k++) {
-          jtag = static_cast<tagint> (buf[j+k]);
-          fprintf(fp," " TAGINT_FORMAT,jtag);
-        }
+        auto mesg = fmt::format(" {} {} {}",itag,itype,numbonds);
+        for (k = 5; k < 5+numbonds; k++)
+          mesg += " " + std::to_string(static_cast<tagint> (buf[j+k]));
         j += (5+numbonds);
 
-        fprintf(fp," " TAGINT_FORMAT,static_cast<tagint> (buf[j]));
+        mesg += " " + std::to_string(static_cast<tagint> (buf[j]));
         j ++;
 
-        for (k = 0; k < numbonds; k++) {
-          abotmp = buf[j+k];
-          fprintf(fp,"%14.3f",abotmp);
-        }
+        for (k = 0; k < numbonds; k++) mesg += fmt::format("{:14.3f}",buf[j+k]);
         j += (1+numbonds);
-        fprintf(fp,"%14.3f%14.3f%14.3f\n",sbotmp,nlptmp,avqtmp);
+
+        mesg += fmt::format("{:14.3f}{:14.3f}{:14.3f}\n",sbotmp,nlptmp,avqtmp);
+        fmt::print(fp, mesg);
       }
     }
   } else {
     MPI_Isend(&buf[0],nbuf_local,MPI_DOUBLE,0,0,world,&irequest2);
     MPI_Wait(&irequest2,MPI_STATUS_IGNORE);
   }
-  if (me ==0) fprintf(fp,"# \n");
+  if (me ==0) fputs("# \n",fp);
 
 }