diff --git a/pyerrors/correlators.py b/pyerrors/correlators.py
index 7d9e2ae0..fa4eb4b1 100644
--- a/pyerrors/correlators.py
+++ b/pyerrors/correlators.py
@@ -218,7 +218,9 @@ class Corr:
         if self.T % 2 != 0:
             raise Exception("Can not symmetrize odd T")
 
-        if not all([o.is_zero_within_error(3) for o in self.content[0]]):
+        test = 1 * self
+        test.gamma_method()
+        if not all([o.is_zero_within_error(3) for o in test.content[0]]):
             warnings.warn("Correlator does not seem to be anti-symmetric around x0=0.", RuntimeWarning)
 
         newcontent = [self.content[0]]
@@ -455,7 +457,9 @@ class Corr:
         T_partner = parity * partner.reverse()
 
         t_slices = []
-        for x0, t_slice in enumerate((self - T_partner).content):
+        test = (self - T_partner)
+        test.gamma_method()
+        for x0, t_slice in enumerate(test.content):
             if t_slice is not None:
                 if not t_slice[0].is_zero_within_error(5):
                     t_slices.append(x0)