diff --git a/bilby/core/result.py b/bilby/core/result.py
index e9d9cb9ef..fadb57d09 100644
--- a/bilby/core/result.py
+++ b/bilby/core/result.py
@@ -1048,15 +1048,14 @@ def get_one_dimensional_median_and_error_bar(self, key, fmt='.2f',
 
         quants_to_compute = np.array([quantiles[0], 0.5, quantiles[1]])
         quants = np.percentile(self.posterior[key], quants_to_compute * 100)
-        summary.median = quants[1]
-        summary.plus = quants[2] - summary.median
-        summary.minus = summary.median - quants[0]
+        median = quants[1]
+        plus = quants[2] - median
+        minus = median - quants[0]
 
         fmt = "{{0:{0}}}".format(fmt).format
         string_template = r"${{{0}}}_{{-{1}}}^{{+{2}}}$"
-        summary.string = string_template.format(
-            fmt(summary.median), fmt(summary.minus), fmt(summary.plus))
-        return summary
+        string = string_template.format(fmt(median), fmt(minus), fmt(plus))
+        return summary(median, minus, plus, string)
 
     @latex_plot_format
     def plot_single_density(self, key, prior=None, cumulative=False,
diff --git a/test/core/result_test.py b/test/core/result_test.py
index dc13a20e8..139e6be25 100644
--- a/test/core/result_test.py
+++ b/test/core/result_test.py
@@ -6,6 +6,7 @@
 import json
 import parameterized
 import pytest
+from collections import namedtuple
 from unittest.mock import patch
 
 import bilby
@@ -622,6 +623,18 @@ class NotAResult(bilby.core.result.Result):
         # so should a result loaded from cache
         assert isinstance(cached_result, NotAResult)
 
+    def test_get_one_dimensional_median_and_error_bar(self):
+        """
+        Test that this method returns an object with the correct structure.
+        """
+        summary = self.result.get_one_dimensional_median_and_error_bar("x")
+
+        assert isinstance(summary, namedtuple)
+        assert isinstance(summary.median, float)
+        assert isinstance(summary.lower, float)
+        assert isinstance(summary.upper, float)
+        assert isinstance(summary.string, str)
+
 
 class TestResultListError(unittest.TestCase):
     def setUp(self):