diff --git a/pyerrors/input/json.py b/pyerrors/input/json.py
index 6b854874..cdf203f2 100644
--- a/pyerrors/input/json.py
+++ b/pyerrors/input/json.py
@@ -171,6 +171,9 @@ def create_json_string(ol, description='', indent=1):
             names.append(key)
             idl.append(value)
         my_obs = Obs(samples, names, idl)
+        my_obs._covobs = obs._covobs
+        for name in obs._covobs:
+            my_obs.names.append(name)
         my_obs.reweighted = obs.reweighted
         my_obs.is_merged = obs.is_merged
         return my_obs
diff --git a/tests/json_io_test.py b/tests/json_io_test.py
index f5546d9f..04ccfd9f 100644
--- a/tests/json_io_test.py
+++ b/tests/json_io_test.py
@@ -242,3 +242,12 @@ def test_json_dict_io():
         jsonio.dump_dict_to_json(od, fname, description=desc)
 
     os.remove(fname + '.json.gz')
+
+
+def test_renorm_deriv_of_corr(tmp_path):
+    c = pe.Corr([pe.pseudo_Obs(i, .1, 'test') for i in range(10)])
+    c *= pe.cov_Obs(1., .1, '#ren')
+    c = c.deriv()
+    pe.input.json.dump_to_json(c, (tmp_path / 'test').as_posix())
+    recover = pe.input.json.load_json((tmp_path / 'test').as_posix())
+    assert np.all([o == 0 for o in (c - recover)[1:-1]])