diff --git a/pyerrors/correlators.py b/pyerrors/correlators.py
index a8d2361e..b9a4f440 100644
--- a/pyerrors/correlators.py
+++ b/pyerrors/correlators.py
@@ -727,9 +727,7 @@ class Corr:
         if variant == 'log':
             newcontent = []
             for t in range(self.T - 1):
-                if ((self.content[t] is None) or (self.content[t + 1] is None)) or (self.content[t + 1][0].value == 0):
-                    newcontent.append(None)
-                elif self.content[t][0].value / self.content[t + 1][0].value < 0:
+                if ((self.content[t] is None) or (self.content[t + 1] is None)) or (self.content[t + 1][0].value == 0) or self.content[t][0].value / self.content[t + 1][0].value < 0:
                     newcontent.append(None)
                 else:
                     newcontent.append(self.content[t] / self.content[t + 1])
@@ -741,9 +739,7 @@ class Corr:
         elif variant == 'logsym':
             newcontent = []
             for t in range(1, self.T - 1):
-                if ((self.content[t - 1] is None) or (self.content[t + 1] is None)) or (self.content[t + 1][0].value == 0):
-                    newcontent.append(None)
-                elif self.content[t - 1][0].value / self.content[t + 1][0].value < 0:
+                if ((self.content[t - 1] is None) or (self.content[t + 1] is None)) or (self.content[t + 1][0].value == 0) or self.content[t - 1][0].value / self.content[t + 1][0].value < 0:
                     newcontent.append(None)
                 else:
                     newcontent.append(self.content[t - 1] / self.content[t + 1])
@@ -872,7 +868,6 @@ class Corr:
             raise ValueError("Start and end point must define a range in the interval 0,T")
 
         self.prange = prange
-        return
 
     def show(self, x_range=None, comp=None, y_range=None, logscale=False, plateau=None, fit_res=None, fit_key=None, ylabel=None, save=None, auto_gamma=False, hide_sigma=None, references=None, title=None):
         """Plots the correlator using the tag of the correlator as label if available.
diff --git a/pyerrors/obs.py b/pyerrors/obs.py
index 69a05bdf..8e6fc757 100644
--- a/pyerrors/obs.py
+++ b/pyerrors/obs.py
@@ -364,7 +364,6 @@ class Obs:
             self.ddvalue = 0.0
         else:
             self.ddvalue = np.sqrt(self.ddvalue) / self._dvalue
-        return
 
     gm = gamma_method
 
@@ -1303,7 +1302,7 @@ def derived_observable(func, data, array_mode=False, **kwargs):
         options = {
             'base_step': 0.1,
             'step_ratio': 2.5}
-        for key in options.keys():
+        for key in options:
             kwarg = kwargs.get(key)
             if kwarg is not None:
                 options[key] = kwarg
diff --git a/pyproject.toml b/pyproject.toml
index a78c2bc0..26a56cb0 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -6,7 +6,7 @@ build-backend = "setuptools.build_meta"
 target-version = "py310"
 
 [tool.ruff.lint]
-extend-select = ["E", "W", "I", "B", "PIE", "PLE", "PLW", "UP", "NPY", "RUF"]
+select = ["E", "W", "I", "B", "PIE", "PLE", "PLW", "UP", "NPY", "RUF"]
 ignore = [
     "F403",     # star imports in __init__ files are intentional
     "E501",     # line too long