diff --git a/fastpt/FASTPT.py b/fastpt/FASTPT.py
index 59b8af2..aae72d4 100644
--- a/fastpt/FASTPT.py
+++ b/fastpt/FASTPT.py
@@ -564,7 +564,7 @@ def IA_mix(self, P, P_window=None, C_window=None):
         if (self.extrap):
             _, P_DBB = self.EK.PK_original(P_DBB)
 
-        return 2 * P_A, P_Btype2, 2 * P_DEE, 2 * P_DBB
+        return 2 * P_A, 4 * P_Btype2, 2 * P_DEE, 2 * P_DBB
 
     ## eq 18; eq 19; eq 27 EE; eq 27 BB