diff --git a/CHANGELOG.md b/CHANGELOG.md
index eba36613b1073e675940021d0ea105918db4e34e..be96fc7d57bd39cb8accd51c9e466f6b2fb42f2d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,11 @@
 # Changelog
 All notable changes to Pulselib will be documented in this file.
 
+## \[1.5.5] - 2022-09-27
+
+### Fixed
+- Incorrect setpoints in measurement_param.add_derived_param.
+
 ## \[1.5.4] - 2022-09-23
 
 ### Added
diff --git a/pulse_lib/acquisition/measurement_converter.py b/pulse_lib/acquisition/measurement_converter.py
index c3d816f998250dca0d591dc1e3f1138ca1347e3b..79693d53a7dcf98db9f57d06f418dc0831aa789e 100644
--- a/pulse_lib/acquisition/measurement_converter.py
+++ b/pulse_lib/acquisition/measurement_converter.py
@@ -131,7 +131,7 @@ class MeasurementParameter(MultiParameter):
                 time = tuple(np.arange(n_samples) * period)
                 setpoints.append(time, 'time', 'time', 'ns')
 
-            self.setpoints = self.setpoints + setpoints.setpoints
+            self.setpoints = self.setpoints + (setpoints.setpoints,)
             self.setpoint_names = self.setpoint_names + (setpoints.setpoint_names,)
             self.setpoint_labels = self.setpoint_labels + (setpoints.setpoint_labels,)
             self.setpoint_units = self.setpoint_units + (setpoints.setpoint_units,)