diff --git a/src/USER-PHONON/dynamical_matrix.cpp b/src/USER-PHONON/dynamical_matrix.cpp
index cef59b3a63..372f4e4e31 100644
--- a/src/USER-PHONON/dynamical_matrix.cpp
+++ b/src/USER-PHONON/dynamical_matrix.cpp
@@ -316,9 +316,10 @@ void DynamicalMatrix::calculateMatrix()
 
 void DynamicalMatrix::writeMatrix(double **dynmat)
 {
-    if (me != 0)
-        return;
+    if (me != 0 || fp == NULL) return;
+
     // print file comment lines
+
     if (!binaryflag && fp) {
         clearerr(fp);
         for (int i = 0; i < 3; i++) {
diff --git a/src/USER-PHONON/dynamical_matrix.h b/src/USER-PHONON/dynamical_matrix.h
index 187968c8f7..56de814e97 100644
--- a/src/USER-PHONON/dynamical_matrix.h
+++ b/src/USER-PHONON/dynamical_matrix.h
@@ -54,10 +54,10 @@ namespace LAMMPS_NS {
         double conv_mass;
         double del;
         int igroup,groupbit;
-        int gcount;  // number of atoms in group
+        bigint gcount;             // number of atoms in group
+        bigint dynlen;             // rank of dynamical matrix
         int scaleflag;
         int me;
-        bigint dynlen;
         int *groupmap;
 
         int compressed;            // 1 if dump file is written compressed, 0 no
@@ -71,4 +71,4 @@ namespace LAMMPS_NS {
 
 
 #endif //LMP_DYNAMICAL_MATRIX_H
-#endif
\ No newline at end of file
+#endif