diff --git a/posydon/binary_evol/DT/step_detached.py b/posydon/binary_evol/DT/step_detached.py
index c41f9bb75b..cd3b107ac1 100644
--- a/posydon/binary_evol/DT/step_detached.py
+++ b/posydon/binary_evol/DT/step_detached.py
@@ -387,7 +387,8 @@ def __init__(
                 "surface_he4",
                 "surface_h1",
                 "log_R",
-                "center_c12"
+                "center_c12",
+                "co_core_mass"
             ]
         )