diff --git a/pyerrors/input/json.py b/pyerrors/input/json.py
index a6060d5f..c4c2aa4b 100644
--- a/pyerrors/input/json.py
+++ b/pyerrors/input/json.py
@@ -358,7 +358,7 @@ def _parse_json_dict(json_dict, verbose=True, full_output=False):
             ret = Obs([[ddi[0] + values[0] for ddi in di] for di in od['deltas']], od['names'], idl=od['idl'])
             ret.is_merged = od['is_merged']
         else:
-            ret = Obs([], [])
+            ret = Obs([], [], means=[])
             ret._value = values[0]
         for name in cd:
             co = cd[name][0]
@@ -383,7 +383,7 @@ def _parse_json_dict(json_dict, verbose=True, full_output=False):
                 ret.append(Obs([list(di[:, i] + values[i]) for di in od['deltas']], od['names'], idl=od['idl']))
                 ret[-1].is_merged = od['is_merged']
             else:
-                ret.append(Obs([], []))
+                ret.append(Obs([], [], means=[]))
                 ret[-1]._value = values[i]
                 print('Created Obs with means= ', values[i])
             for name in cd:
@@ -410,7 +410,7 @@ def _parse_json_dict(json_dict, verbose=True, full_output=False):
                 ret.append(Obs([di[:, i] + values[i] for di in od['deltas']], od['names'], idl=od['idl']))
                 ret[-1].is_merged = od['is_merged']
             else:
-                ret.append(Obs([], []))
+                ret.append(Obs([], [], means=[]))
                 ret[-1]._value = values[i]
             for name in cd:
                 co = cd[name][i]
diff --git a/pyerrors/obs.py b/pyerrors/obs.py
index cdf7bce8..1d459247 100644
--- a/pyerrors/obs.py
+++ b/pyerrors/obs.py
@@ -94,41 +94,40 @@ class Obs:
         self.N = 0
         self.is_merged = {}
         self.idl = {}
-        if len(samples):
-            if idl is not None:
-                for name, idx in sorted(zip(names, idl)):
-                    if isinstance(idx, range):
-                        self.idl[name] = idx
-                    elif isinstance(idx, (list, np.ndarray)):
-                        dc = np.unique(np.diff(idx))
-                        if np.any(dc < 0):
-                            raise Exception("Unsorted idx for idl[%s]" % (name))
-                        if len(dc) == 1:
-                            self.idl[name] = range(idx[0], idx[-1] + dc[0], dc[0])
-                        else:
-                            self.idl[name] = list(idx)
+        if idl is not None:
+            for name, idx in sorted(zip(names, idl)):
+                if isinstance(idx, range):
+                    self.idl[name] = idx
+                elif isinstance(idx, (list, np.ndarray)):
+                    dc = np.unique(np.diff(idx))
+                    if np.any(dc < 0):
+                        raise Exception("Unsorted idx for idl[%s]" % (name))
+                    if len(dc) == 1:
+                        self.idl[name] = range(idx[0], idx[-1] + dc[0], dc[0])
                     else:
-                        raise Exception('incompatible type for idl[%s].' % (name))
-            else:
-                for name, sample in sorted(zip(names, samples)):
-                    self.idl[name] = range(1, len(sample) + 1)
+                        self.idl[name] = list(idx)
+                else:
+                    raise Exception('incompatible type for idl[%s].' % (name))
+        else:
+            for name, sample in sorted(zip(names, samples)):
+                self.idl[name] = range(1, len(sample) + 1)
 
-            if kwargs.get("means") is not None:
-                for name, sample, mean in sorted(zip(names, samples, kwargs.get("means"))):
-                    self.shape[name] = len(self.idl[name])
-                    self.N += self.shape[name]
-                    self.r_values[name] = mean
-                    self.deltas[name] = sample
-            else:
-                for name, sample in sorted(zip(names, samples)):
-                    self.shape[name] = len(self.idl[name])
-                    self.N += self.shape[name]
-                    if len(sample) != self.shape[name]:
-                        raise Exception('Incompatible samples and idx for %s: %d vs. %d' % (name, len(sample), self.shape[name]))
-                    self.r_values[name] = np.mean(sample)
-                    self.deltas[name] = sample - self.r_values[name]
-                    self._value += self.shape[name] * self.r_values[name]
-                self._value /= self.N
+        if kwargs.get("means") is not None:
+            for name, sample, mean in sorted(zip(names, samples, kwargs.get("means"))):
+                self.shape[name] = len(self.idl[name])
+                self.N += self.shape[name]
+                self.r_values[name] = mean
+                self.deltas[name] = sample
+        else:
+            for name, sample in sorted(zip(names, samples)):
+                self.shape[name] = len(self.idl[name])
+                self.N += self.shape[name]
+                if len(sample) != self.shape[name]:
+                    raise Exception('Incompatible samples and idx for %s: %d vs. %d' % (name, len(sample), self.shape[name]))
+                self.r_values[name] = np.mean(sample)
+                self.deltas[name] = sample - self.r_values[name]
+                self._value += self.shape[name] * self.r_values[name]
+            self._value /= self.N
 
         self._dvalue = 0.0
         self.ddvalue = 0.0
@@ -1522,7 +1521,7 @@ def cov_Obs(means, cov, name, grad=None):
         co : Covobs
             Covobs to be embedded into the Obs
         """
-        o = Obs([], [])
+        o = Obs([], [], means=[])
         o._value = co.value
         o.names.append(co.name)
         o._covobs[co.name] = co
diff --git a/tests/obs_test.py b/tests/obs_test.py
index 2fed00af..14f18c81 100644
--- a/tests/obs_test.py
+++ b/tests/obs_test.py
@@ -653,7 +653,7 @@ def test_covariance_symmetry():
 
 def test_empty_obs():
     o = pe.Obs([np.random.rand(100)], ['test'])
-    q = o + pe.Obs([], [])
+    q = o + pe.Obs([], [], means=[])
     assert q == o
 
 
@@ -704,4 +704,4 @@ def test_merge_idx():
     new_idx = pe.obs._merge_idx(idl)
     assert(new_idx[-1] > new_idx[0])
     for i in range(1, len(new_idx)):
-        assert(new_idx[i - 1] < new_idx[i])
\ No newline at end of file
+        assert(new_idx[i - 1] < new_idx[i])