diff --git a/src/qibocal/protocols/flux_dependence/qubit_flux_dependence.py b/src/qibocal/protocols/flux_dependence/qubit_flux_dependence.py
index e2a464285..1cebfaeea 100644
--- a/src/qibocal/protocols/flux_dependence/qubit_flux_dependence.py
+++ b/src/qibocal/protocols/flux_dependence/qubit_flux_dependence.py
@@ -218,12 +218,12 @@ def fit_function(x, w_max, normalization, offset):
                 "charging_energy": data.charging_energy[qubit] * HZ_TO_GHZ,
             }
             frequency[qubit] = popt[0] * GHZ_TO_HZ
-            middle_freq = np.median(frequencies)
+            middle_bias = np.median(biases)
             # solution to x*popt[1] + popt[2] = k
             # such that x is close to 0
             # to avoid errors due to periodicity
             sweetspot[qubit] = (
-                np.round(popt[1] * middle_freq + popt[2]) - popt[2]
+                np.round(popt[1] * middle_bias + popt[2]) - popt[2]
             ) / popt[1]
             matrix_element[qubit] = popt[1]
         except ValueError as e: