diff --git a/src/fix_respa.h b/src/fix_respa.h
index 052cef594b..066a3bd480 100644
--- a/src/fix_respa.h
+++ b/src/fix_respa.h
@@ -27,6 +27,7 @@ namespace LAMMPS_NS {
 class FixRespa : public Fix {
   friend class Respa;
   friend class FixShake;
+  friend class FixShake2;
 
  public:
   FixRespa(class LAMMPS *, int, char **);