diff --git a/src/USER-VTK/dump_vtk.cpp b/src/USER-VTK/dump_vtk.cpp
index 4a0c1618a6..78be5668cf 100644
--- a/src/USER-VTK/dump_vtk.cpp
+++ b/src/USER-VTK/dump_vtk.cpp
@@ -167,6 +167,13 @@ DumpVTK::DumpVTK(LAMMPS *lmp, int narg, char **arg) :
   header_choice = NULL;
   write_choice = NULL;
   boxcorners = NULL;
+
+  // unsupported feature by dump vtk
+  delete [] vformat;
+  vformat = NULL;
+
+  delete [] format_column_user;
+  format_column_user = NULL;
 }
 
 /* ---------------------------------------------------------------------- */
diff --git a/src/dump_custom.cpp b/src/dump_custom.cpp
index 44842619fe..9df0264e55 100644
--- a/src/dump_custom.cpp
+++ b/src/dump_custom.cpp
@@ -244,11 +244,15 @@ DumpCustom::~DumpCustom()
   for (int i = 1; i <= ntypes; i++) delete [] typenames[i];
   delete [] typenames;
 
-  for (int i = 0; i < size_one; i++) delete [] vformat[i];
-  delete [] vformat;
+  if(vformat) {
+    for (int i = 0; i < size_one; i++) delete [] vformat[i];
+    delete [] vformat;
+  }
 
-  for (int i = 0; i < size_one; i++) delete [] format_column_user[i];
-  delete [] format_column_user;
+  if(format_column_user) {
+    for (int i = 0; i < size_one; i++) delete [] format_column_user[i];
+    delete [] format_column_user;
+  }
 
   delete [] columns;
 }