diff --git a/cost_function.py b/cost_function.py
index 571bc8aafb1a3df227b947175580a3fca523655d..4fc4ff2a20cd5a47e8481702f8d628d7e0793184 100755
--- a/cost_function.py
+++ b/cost_function.py
@@ -110,8 +110,8 @@ t1 = time.perf_counter()
 timings.write(f"loading: {t1 - t0:.0f} s\n")
 t0 = t1
 
-g.vp['pos_first'] = g.new_vp('object')
-g.vp['pos_last'] = g.new_vp('object')
+g.vp['pos_first'] = g.new_vp('vector<double>')
+g.vp['pos_last'] = g.new_vp('vector<double>')
 g.vp['first_av_rad'] = g.new_vp('float')
 g.vp['first_av_ros'] = g.new_vp('float')
 g.vp['last_av_rad'] = g.new_vp('float')