diff --git a/pyerrors/obs.py b/pyerrors/obs.py
index bf8575bd..6874bd12 100644
--- a/pyerrors/obs.py
+++ b/pyerrors/obs.py
@@ -582,7 +582,7 @@ class Obs:
         ensemble to the error and returns a dictionary containing the fractions."""
         if not hasattr(self, 'e_dvalue'):
             raise Exception('Run the gamma method first.')
-        if self._dvalue == 0.0:
+        if np.isclose(0.0, self._dvalue, atol=1e-15):
             raise Exception('Error is 0.0')
         labels = self.e_names
         sizes = [self.e_dvalue[name] ** 2 for name in labels] / self._dvalue ** 2
@@ -729,6 +729,9 @@ class Obs:
     def __rsub__(self, y):
         return -1 * (self - y)
 
+    def __pos__(self):
+        return self
+
     def __neg__(self):
         return -1 * self
 
@@ -911,8 +914,11 @@ class CObs:
     def __abs__(self):
         return np.sqrt(self.real**2 + self.imag**2)
 
-    def __neg__(other):
-        return -1 * other
+    def __pos__(self):
+        return self
+
+    def __neg__(self):
+        return -1 * self
 
     def __eq__(self, other):
         return self.real == other.real and self.imag == other.imag
diff --git a/tests/linalg_test.py b/tests/linalg_test.py
index 61c71514..09db0ac5 100644
--- a/tests/linalg_test.py
+++ b/tests/linalg_test.py
@@ -314,6 +314,9 @@ def test_matrix_functions():
     # Check determinant
     assert pe.linalg.det(np.diag(np.diag(matrix))) == np.prod(np.diag(matrix))
 
+    with pytest.raises(Exception):
+        pe.linalg.det(5)
+
     pe.linalg.pinv(matrix[:,:3])
 
 
@@ -347,3 +350,10 @@ def test_complex_matrix_operations():
         diff = ta * tb - 1
         for (i, j), entry in np.ndenumerate(diff):
             assert entry.is_zero()
+
+
+def test_complex_matrix_real_entries():
+    my_mat = get_complex_matrix(4)
+    my_mat[0, 1] = 4
+    my_mat[2, 0] = pe.Obs([np.random.normal(1.0, 0.1, 100)], ['t'])
+    assert np.all((my_mat @ pe.linalg.inv(my_mat) - np.identity(4)) == 0)
diff --git a/tests/obs_test.py b/tests/obs_test.py
index 4eae6db4..c8aef487 100644
--- a/tests/obs_test.py
+++ b/tests/obs_test.py
@@ -51,6 +51,12 @@ def test_Obs_exceptions():
     my_obs.gamma_method()
     my_obs.details()
 
+    obs = pe.Obs([np.random.normal(1.0, 0.1, 100)], ['t'])
+    one = obs / obs
+    one.gamma_method()
+    with pytest.raises(Exception):
+        one.plot_piechart()
+
 def test_dump():
     value = np.random.normal(5, 10)
     dvalue = np.abs(np.random.normal(0, 1))
@@ -86,6 +92,8 @@ def test_comparison():
     assert test_obs2 != value2
     assert test_obs1 != test_obs2
     assert test_obs2 != test_obs1
+    assert +test_obs1 == test_obs1
+    assert -test_obs1 == 0 - test_obs1
 
 
 def test_function_overloading():
@@ -367,6 +375,8 @@ def test_cobs():
     obs2 = pe.pseudo_Obs(-0.2, 0.03, 't')
 
     my_cobs = pe.CObs(obs1, obs2)
+    assert +my_cobs == my_cobs
+    assert -my_cobs == 0 - my_cobs
     my_cobs == my_cobs
     str(my_cobs)
     repr(my_cobs)
@@ -758,3 +768,15 @@ def test_merge_idx():
     assert(new_idx[-1] > new_idx[0])
     for i in range(1, len(new_idx)):
         assert(new_idx[i - 1] < new_idx[i])
+
+def test_cobs_array():
+    cobs = pe.Obs([np.random.normal(1.0, 0.1, 100)], ['t']) * (1 + 2j)
+    np.identity(4) + cobs
+    cobs + np.identity(4)
+    np.identity(4) - cobs
+    cobs - np.identity(4)
+    np.identity(4) * cobs
+    cobs * np.identity(4)
+    np.identity(4) / cobs
+    cobs / np.ones((4, 4))
+