diff --git a/pyerrors/correlators.py b/pyerrors/correlators.py
index 4f528ec8..a655d36b 100644
--- a/pyerrors/correlators.py
+++ b/pyerrors/correlators.py
@@ -201,8 +201,9 @@ def symmetric(self):
         if self.T % 2 != 0:
             raise Exception("Can not symmetrize odd T")
 
-        if np.argmax(np.abs(self.content)) != 0:
-            warnings.warn("Correlator does not seem to be symmetric around x0=0.", RuntimeWarning)
+        if self.content[0] is not None:
+            if np.argmax(np.abs([o[0].value if o is not None else 0 for o in self.content])) != 0:
+                warnings.warn("Correlator does not seem to be symmetric around x0=0.", RuntimeWarning)
 
         newcontent = [self.content[0]]
         for t in range(1, self.T):
diff --git a/tests/correlators_test.py b/tests/correlators_test.py
index 0b408ba0..cc08544c 100644
--- a/tests/correlators_test.py
+++ b/tests/correlators_test.py
@@ -552,3 +552,17 @@ def test_corr_no_filtering():
     b = pe.pseudo_Obs(1, 1e-11, 'a', samples=30)
     c *= b
     assert np.all([c[0].idl == o.idl for o in c])
+
+
+def test_corr_symmetric():
+    obs = []
+    for _ in range(4):
+        obs.append(pe.pseudo_Obs(np.random.rand(), 0.1, "test"))
+
+    for corr in [pe.Corr([obs[0] + 8, obs[1], obs[2], obs[3]]),
+                 pe.Corr([obs[0] + 8, obs[1], obs[2], None]),
+                 pe.Corr([None, obs[1], obs[2], obs[3]])]:
+        scorr = corr.symmetric()
+        assert scorr[1] == scorr[3]
+        assert scorr[2] == corr[2]
+        assert scorr[0] == corr[0]