diff --git a/bilby/core/result.py b/bilby/core/result.py
index 873ac2e31b5e0e5bfbfa841d2dab517c741baebd..f643d919e9483bb3b0e3237d390fdf4a784a988a 100644
--- a/bilby/core/result.py
+++ b/bilby/core/result.py
@@ -1277,13 +1277,16 @@ class ResultList(list):
         return posteriors, result
 
     def _check_nested_samples(self):
-        if not np.all([res.nested_samples is not None for res in self]):
-            raise CombineResultError("Cannot combine results: No nested samples available "
-                                     "in all results")
+        for res in self:
+            try:
+                res.nested_samples
+            except ValueError:
+                raise CombineResultError("Cannot combine results: No nested samples available "
+                                         "in all results")
 
     def _check_consistent_priors(self):
         for res in self:
-            for p in self[0].search_parameter_keys:
+            for p in self[0].priors.keys():
                 if not self[0].priors[p] == res.priors[p] or len(self[0].priors) != len(res.priors):
                     raise CombineResultError("Cannot combine results: inconsistent priors")
 
diff --git a/test/result_test.py b/test/result_test.py
index 64b7d51a09709065bbaa66cbca561a6099236f5e..049c9d4076e535b18bac2932de558918ab077536 100644
--- a/test/result_test.py
+++ b/test/result_test.py
@@ -524,6 +524,8 @@ class TestResultList(unittest.TestCase):
         result.log_evidence_err = 11
         result.log_bayes_factor = 12
         result.log_noise_evidence = 13
+        result._nested_samples = None
+        self.nested_results.append(result)
         with self.assertRaises(bilby.result.CombineResultError):
             self.nested_results.combine()