diff --git a/src/USER-PHONON/fix_phonon.cpp b/src/USER-PHONON/fix_phonon.cpp
index cf56117892..3a37c67a38 100644
--- a/src/USER-PHONON/fix_phonon.cpp
+++ b/src/USER-PHONON/fix_phonon.cpp
@@ -668,7 +668,8 @@ void FixPhonon::postprocess( )
   }
 
   // to get Phi = KT.G^-1; normalization of FFTW data is done here
-  double boltz = force->boltz, kbtsqrt[sysdim], TempAve = 0.;
+  double boltz = force->boltz, TempAve = 0.;
+  double *kbtsqrt = new double[sysdim];
   double TempFac = inv_neval * inv_nTemp;
   double NormFac = TempFac * double(ntotal);
 
@@ -692,7 +693,7 @@ void FixPhonon::postprocess( )
   MPI_Gatherv(Phi_q[0],mynq*fft_dim2*2,MPI_DOUBLE,Phi_all[0],recvcnts,displs,MPI_DOUBLE,0,world);
 
   // to collect all basis info and averaged it on root
-  double basis_root[fft_dim];
+  double *basis_root = new double[fft_dim];
   if (fft_dim > sysdim) MPI_Reduce(&basis[1][0], &basis_root[sysdim], fft_dim-sysdim, MPI_DOUBLE, MPI_SUM, 0, world);
 
   if (me == 0){ // output dynamic matrix by root
@@ -772,7 +773,8 @@ void FixPhonon::postprocess( )
     }
     fflush(flog);
   }
-
+  delete[] kbtsqrt;
+  delete[] basis_root;
 }   // end of postprocess
 
 /* ----------------------------------------------------------------------