diff --git a/src/toolbox_scs/detectors/hrixs.py b/src/toolbox_scs/detectors/hrixs.py
index 63bce3454083712d22df687637b8635ecd2fa699..3dabbdd73be14cec52e408c9d3a4c49ae501e72e 100644
--- a/src/toolbox_scs/detectors/hrixs.py
+++ b/src/toolbox_scs/detectors/hrixs.py
@@ -398,7 +398,7 @@ class hRIXS:
         Example
         -------
 
-            data = h.centroid(data)  # find photons in all images of the run
+            h.centroid(data)  # find photons in all images of the run
             data.spectrum[0, :].plot()  # plot the spectrum of the first image
         """
         if bins is None:
@@ -497,7 +497,7 @@ class hRIXS:
         Example
         -------
 
-            data = h.centroid(data)  # create spectra from finding photons
+            h.centroid(data)  # create spectra from finding photons
             agg = h.aggregate(data)  # sum all spectra
             agg.spectrum.plot()  # plot the resulting spectrum
 
diff --git a/src/toolbox_scs/test/test_hrixs.py b/src/toolbox_scs/test/test_hrixs.py
index 0a78db7597f8adb9188a260ead53c5f29c48ef9b..7b75cdef6a103f53f033645b34f15fba979f8588 100644
--- a/src/toolbox_scs/test/test_hrixs.py
+++ b/src/toolbox_scs/test/test_hrixs.py
@@ -53,7 +53,8 @@ class TestHRIXS(unittest.TestCase):
         ])
         h.CURVE_A = 0.1
         h.CURVE_B = 0.01
-        data = h.centroid(data)
+        r = h.centroid(data)
+        self.assertIs(r, data)
         assert_array_equal(data['spectrum'], [
             [0, 0, 0, 1, 0, 0, 0, 0, 0, 0],
             [0, 0, 0, 1, 0, 0, 0, 0, 0, 0],