diff --git a/pyerrors/misc.py b/pyerrors/misc.py
index bbfb8e7d..cf0dd18a 100644
--- a/pyerrors/misc.py
+++ b/pyerrors/misc.py
@@ -105,16 +105,11 @@ def gen_correlated_data(means, cov, name, tau=0.5, samples=1000):
 
 
 def _assert_equal_properties(ol, otype=Obs):
-    if not isinstance(ol[0], otype):
-        raise Exception("Wrong data type in list.")
+    otype = type(ol[0])
     for o in ol[1:]:
         if not isinstance(o, otype):
             raise Exception("Wrong data type in list.")
-        if not ol[0].is_merged == o.is_merged:
-            raise Exception("All Obs in list have to have the same state 'is_merged'.")
-        if not ol[0].reweighted == o.reweighted:
-            raise Exception("All Obs in list have to have the same property 'reweighted'.")
-        if not ol[0].e_content == o.e_content:
-            raise Exception("All Obs in list have to be defined on the same set of configs.")
-        if not ol[0].idl == o.idl:
-            raise Exception("All Obs in list have to be defined on the same set of configurations.")
+        for attr in ["is_merged", "reweighted", "e_content", "idl"]:
+            if hasattr(ol[0], attr):
+                if not getattr(ol[0], attr) == getattr(o, attr):
+                    raise Exception(f"All Obs in list have to have the same state '{attr}'.")