diff --git a/engines/fortran/main.f90 b/engines/fortran/main.f90
index c6c1f46..0d9e909 100644
--- a/engines/fortran/main.f90
+++ b/engines/fortran/main.f90
@@ -1042,11 +1042,11 @@ subroutine write_json(outdir, tx, ty, tz, tvx, tvy, tvz, &
     if (nb > 0) then
         call write_int2_arr(u, 'bond_pairs', bp, nb, .true.)
         call write_dbl_arr(u, 'bond_stiffness', bk, nb, .true.)
-        call write_dbl_arr(u, 'bond_rest_lengths', br, nb, .false.)
+        call write_dbl_arr(u, 'bond_rest_lengths', br, nb, .true.)
     else
         write(u, '(a)') '  "bond_pairs": [],'
         write(u, '(a)') '  "bond_stiffness": [],'
-        write(u, '(a)') '  "bond_rest_lengths": []'
+        write(u, '(a)') '  "bond_rest_lengths": [],'
     end if
 
     write(buf, '(a, i0)') '  "driving_force": ', driving_force