diff --git a/src/fix_spring_self.cpp b/src/fix_spring_self.cpp
index 550b3afc4d..31f54caef2 100644
--- a/src/fix_spring_self.cpp
+++ b/src/fix_spring_self.cpp
@@ -73,6 +73,7 @@ FixSpringSelf::FixSpringSelf(LAMMPS *lmp, int narg, char **arg) :
   // register with Atom class
 
   xoriginal = nullptr;
+  maxatom = atom->nmax;
   FixSpringSelf::grow_arrays(atom->nmax);
   atom->add_callback(Atom::GROW);
   atom->add_callback(Atom::RESTART);
diff --git a/src/fix_spring_self.h b/src/fix_spring_self.h
index 59dba78e43..24a03aa92e 100644
--- a/src/fix_spring_self.h
+++ b/src/fix_spring_self.h
@@ -47,11 +47,12 @@ class FixSpringSelf : public Fix {
   int size_restart(int) override;
   int maxsize_restart() override;
 
- private:
+ protected:
   double k, espring;
   double **xoriginal;    // original coords of atoms
   int xflag, yflag, zflag;
   int ilevel_respa;
+  int maxatom;
 };
 
 }    // namespace LAMMPS_NS