diff --git a/megabeast/tools/simulate_obs.py b/megabeast/tools/simulate_obs.py
index d7eb7d6..f204286 100644
--- a/megabeast/tools/simulate_obs.py
+++ b/megabeast/tools/simulate_obs.py
@@ -375,13 +375,6 @@ def simulate_obs(
                 binfo = af.tree
                 age_prior_model = binfo["age_prior_model"]
                 mass_prior_model = binfo["mass_prior_model"]
-        elif ensembleparams is not None:
-            if nsim > 0:
-                age_prior_model = None
-                mass_prior_model = None
-            else:
-                age_prior_model=mbmod.physics_model["logA"],
-                mass_prior_model=mbmod.physics_model["M_ini"],
         else:
             age_prior_model = None
             mass_prior_model = None
@@ -393,6 +386,13 @@ def simulate_obs(
 
             mbmod = MB_Model(mbparams)
 
+            if nsim > 0:
+                age_prior_model = None
+                mass_prior_model = None
+            else:
+                age_prior_model=mbmod.physics_model["logA"],
+                mass_prior_model=mbmod.physics_model["M_ini"],
+
             # mock up a beast spectral grid so that the BEAST code can be used
             cur_physmod = Table()
             for cparam in ["logA", "M_ini", "Z", "distance", "Av", "Rv", "f_A"]: