diff --git a/src/pymodaq_plugins_slmsuite/hardware/slm_controller.py b/src/pymodaq_plugins_slmsuite/hardware/slm_controller.py
index 228c4e6..3b2beaf 100644
--- a/src/pymodaq_plugins_slmsuite/hardware/slm_controller.py
+++ b/src/pymodaq_plugins_slmsuite/hardware/slm_controller.py
@@ -127,5 +127,19 @@ def get_phase(self) -> np.ndarray:
         phase = self.slm.phase
         return np.asarray(phase.get() if hasattr(phase, 'get') else phase)
 
+    def set_wavelength(self, wav_um: float):
+        """Change the working wavelength of the open SLM (microns)
+
+        slmsuite reads ``wav_um`` each time it converts a phase into grey levels. The design wavelength follows it if
+        it was the same (default of slmsuite), keeping ``phase_scaling`` at 1. The Holoeye SDK also has to know it.
+        """
+        old = self.slm.wav_um
+        if self.slm.wav_design_um == old:
+            self.slm.wav_design_um = float(wav_um)
+        self.slm.wav_um = float(wav_um)
+        slm_lib = getattr(self.slm, 'slm_lib', None)
+        if self.slm_type == 'Holoeye' and slm_lib is not None:
+            self.slm._handle_error(slm_lib.setWavelength(wav_um * 1000))
+
     def close(self):
         self.slm.close()
diff --git a/src/pymodaq_plugins_slmsuite/resources/daq_move_SlmsuiteBase.py b/src/pymodaq_plugins_slmsuite/resources/daq_move_SlmsuiteBase.py
index 9c70b18..e1dde92 100644
--- a/src/pymodaq_plugins_slmsuite/resources/daq_move_SlmsuiteBase.py
+++ b/src/pymodaq_plugins_slmsuite/resources/daq_move_SlmsuiteBase.py
@@ -47,7 +47,8 @@ class DAQ_Move_SlmsuiteBase(DAQ_Move_base):
         ]},
         {'title': 'Wavelength (nm):', 'name': 'wavelength_nm', 'type': 'float',
          'value': config('slm', 'wavelength_nm'), 'min': 1.,
-         'tip': 'Working wavelength, used by slmsuite to convert phases into grey levels. Needs a re-initialization.'},
+         'tip': 'Working wavelength, used by slmsuite to convert phases into grey levels. Imposed by the BeamShaping '
+                'extension (setup preference) when it is loaded. A change is applied directly to the open SLM.'},
         {'title': 'Apply phase correction:', 'name': 'phase_correct', 'type': 'bool', 'value': True,
          'tip': 'Add the wavefront correction loaded in slmsuite (if any) to the displayed phases'},
         {'title': 'Input as grey levels:', 'name': 'input_as_grey_levels', 'type': 'bool', 'value': False,
@@ -89,7 +90,8 @@ def close(self):
             self.controller.close()
 
     def commit_settings(self, param: Parameter):
-        pass
+        if param.name() == 'wavelength_nm' and self.controller is not None and self.is_master:
+            self.controller.set_wavelength(param.value() / 1000)
 
     def get_actuator_value(self) -> DataActuator:
         """The phase (radians) that the SLM displays"""
diff --git a/tests/test_slmsuite_plugins.py b/tests/test_slmsuite_plugins.py
index 5594525..751a762 100644
--- a/tests/test_slmsuite_plugins.py
+++ b/tests/test_slmsuite_plugins.py
@@ -255,3 +255,33 @@ def test_holoeye_preview_can_be_enabled(monkeypatch):
 def test_holoeye_sdk_without_preview_option(monkeypatch):
     _open_holoeye(monkeypatch, FakeHEDSWithoutOption)
     assert FakeHEDSWithoutOption.SLM.calls == [('index:0',)]
+
+
+class TestWavelengthUpdate:
+    def test_changed_after_the_init(self, slm):
+        param = slm.settings.child('wavelength_nm')
+        param.setValue(800.)
+        slm.commit_settings(param)  # called by the DAQ_Move when a setting changes
+        slm_object = slm.controller.slm
+        assert slm_object.wav_um == pytest.approx(0.8)
+        assert slm_object.phase_scaling == 1  # design wavelength follows the working one
+
+        # the phase is converted with the new wavelength, without re-initialization
+        slm.controller.show_phase(np.full((HEIGHT, WIDTH), 1.))
+        assert slm.initialized
+
+    def test_design_wavelength_chosen_by_the_user_is_kept(self):
+        controller = SlmController('SimulatedSLM', resolution=(WIDTH, HEIGHT), wav_um=0.5, wav_design_um=1.)
+        controller.set_wavelength(0.8)
+        assert (controller.slm.wav_um, controller.slm.wav_design_um) == (0.8, 1.)
+        controller.close()
+
+    def test_holoeye_sdk_is_told(self):
+        calls = []
+        slm_object = SimpleNamespace(wav_um=0.5, wav_design_um=0.5, _handle_error=calls.append,
+                                     slm_lib=SimpleNamespace(setWavelength=lambda nm: calls.append(nm) or 0))
+        controller = SlmController.__new__(SlmController)
+        controller.slm_type, controller.slm = 'Holoeye', slm_object
+        controller.set_wavelength(0.8)
+        assert calls == [800., 0]
+        assert slm_object.wav_um == 0.8