diff --git a/src/eko/io/runcards.py b/src/eko/io/runcards.py
index 83c1dae95..02d6302e1 100644
--- a/src/eko/io/runcards.py
+++ b/src/eko/io/runcards.py
@@ -183,7 +183,7 @@ def new_theory(self):
             max_num_flavs=old["MaxNfAs"],
         )
         new["heavy"] = {
-            "num_flavs_init": nf_default(old["Qref"] ** 2.0, default_atlas(ms, ks))
+            "num_flavs_init": nf_default(old["Q0"] ** 2.0, default_atlas(ms, ks))
             if old["nf0"] is None
             else old["nf0"],
             "num_flavs_max_pdf": old["MaxNfPdf"],