diff --git a/networks/primordial_chem/pynucastro.net b/networks/primordial_chem/pynucastro.net
index 2bd03cfd6..fb7ea64a5 100644
--- a/networks/primordial_chem/pynucastro.net
+++ b/networks/primordial_chem/pynucastro.net
@@ -12,3 +12,4 @@ hd                 HD       17.0    8.0
 hepp               HEpp     17.0    9.0
 hep                HEp      18.0    9.0
 he                 HE       4.0     2.0
+__aux_Tdust