diff --git a/pyerrors/pyerrors.py b/pyerrors/pyerrors.py
index 555c73d8..5d54b9af 100644
--- a/pyerrors/pyerrors.py
+++ b/pyerrors/pyerrors.py
@@ -655,6 +655,9 @@ class CObs:
         if isinstance(self.imag, Obs):
             self.imag.gamma_method(**kwargs)
 
+    def conjugate(self):
+        return CObs(self.real, -self.imag)
+
     def __add__(self, other):
         if hasattr(other, 'real') and hasattr(other, 'imag'):
             return CObs(self.real + other.real,
@@ -701,7 +704,7 @@ class CObs:
         return self.real == other.real and self.imag == other.imag
 
     def __str__(self):
-        return '(' + str(self.real) + int(self.imag > - np.finfo(np.float64).eps) * '+' + str(self.imag) + 'j)'
+        return '(' + str(self.real) + int(self.imag >= 0.0) * '+' + str(self.imag) + 'j)'
 
     def __repr__(self):
         return 'CObs[' + str(self) + ']'
diff --git a/tests/test_pyerrors.py b/tests/test_pyerrors.py
index bed06530..58ec21f3 100644
--- a/tests/test_pyerrors.py
+++ b/tests/test_pyerrors.py
@@ -199,6 +199,10 @@ def test_cobs():
     obs2 = pe.pseudo_Obs(-0.2, 0.03, 't')
 
     my_cobs = pe.CObs(obs1, obs2)
+    assert not (my_cobs + my_cobs.conjugate()).real.is_zero()
+    assert (my_cobs + my_cobs.conjugate()).imag.is_zero()
+    assert (my_cobs - my_cobs.conjugate()).real.is_zero()
+    assert not (my_cobs - my_cobs.conjugate()).imag.is_zero()
     np.abs(my_cobs)
     fs = [[lambda x: x[0] + x[1], lambda x: x[1] + x[0]],
           [lambda x: x[0] * x[1], lambda x: x[1] * x[0]]]