diff --git a/secop/modules.py b/secop/modules.py
index 5e3ea67..77e8bbc 100644
--- a/secop/modules.py
+++ b/secop/modules.py
@@ -461,8 +461,7 @@ class Module(HasAccessibles):
         if mainvalue:
             mainunit = mainvalue.datatype.unit
             if mainunit:
-                for pname, pobj in self.parameters.items():
-                    pobj.datatype.set_main_unit(mainunit)
+                self.applyMainUnit(mainunit)
 
         # 6) check complete configuration of * properties
         if not errors:
@@ -485,6 +484,11 @@ class Module(HasAccessibles):
     def __getitem__(self, item):
         return self.accessibles.__getitem__(item)
 
+    def applyMainUnit(self, mainunit):
+        """replace $ in units of parameters by mainunit"""
+        for pobj in self.parameters.values():
+            pobj.datatype.set_main_unit(mainunit)
+
     def announceUpdate(self, pname, value=None, err=None, timestamp=None):
         """announce a changed value or readerror"""
 
diff --git a/secop_mlz/entangle.py b/secop_mlz/entangle.py
index df20938..528c9bc 100644
--- a/secop_mlz/entangle.py
+++ b/secop_mlz/entangle.py
@@ -376,6 +376,12 @@ class AnalogInput(PyTangoDevice, Readable):
     """
     The AnalogInput handles all devices only delivering an analogue value.
     """
+    __main_unit = None
+
+    def applyMainUnit(self, mainunit):
+        # called from __init__ method
+        # replacement of '$' by main unit must be done later
+        self.__main_unit = mainunit
 
     def startModule(self, start_events):
         super().startModule(start_events)
@@ -386,8 +392,11 @@ class AnalogInput(PyTangoDevice, Readable):
             # update
             if attrInfo.unit != 'No unit':
                 self.accessibles['value'].datatype.setProperty('unit', attrInfo.unit)
+                self.__main_unit = attrInfo.unit
         except Exception as e:
             self.log.error(e)
+        if self.__main_unit:
+            super().applyMainUnit(self.__main_unit)
 
     def read_value(self):
         return self._dev.value
diff --git a/test/test_modules.py b/test/test_modules.py
index 007a1ed..cbe43e5 100644
--- a/test/test_modules.py
+++ b/test/test_modules.py
@@ -659,3 +659,39 @@ def test_problematic_value_range():
     obj = Mod4('obj', logger, {
         'value.min': 0, 'value.max': 10,
         'target.min': 0, 'target.max': 10, 'description': ''}, srv)
+
+
+@pytest.mark.parametrize('config, dynamicunit, finalunit, someunit', [
+    ({}, 'K', 'K', 'K'),
+    ({'value.unit': 'K'}, 'C', 'C', 'C'),
+    ({'value.unit': 'K'}, '', 'K', 'K'),
+    ({'value.unit': 'K', 'someparam.unit': 'A'}, 'C', 'C', 'A'),
+])
+def test_deferred_main_unit(config, dynamicunit, finalunit, someunit):
+    # this pattern is used in secop_mlz.entangle.AnalogInput
+    class Mod(Drivable):
+        ramp = Parameter('', datatype=FloatRange(unit='$/min'))
+        someparam = Parameter('', datatype=FloatRange(unit='$'))
+        __main_unit = None
+
+        def applyMainUnit(self, mainunit):
+            # called from __init__ method
+            # replacement of '$' by main unit must be done later
+            self.__main_unit = mainunit
+
+        def startModule(self, start_events):
+            super().startModule(start_events)
+            if dynamicunit:
+                self.accessibles['value'].datatype.setProperty('unit', dynamicunit)
+                self.__main_unit = dynamicunit
+            if self.__main_unit:
+                super().applyMainUnit(self.__main_unit)
+
+    srv = ServerStub({})
+    m = Mod('m', logger, {'description': '', **config}, srv)
+    m.startModule(None)
+    assert m.parameters['value'].datatype.unit == finalunit
+    assert m.parameters['target'].datatype.unit == finalunit
+    assert m.parameters['ramp'].datatype.unit == finalunit + '/min'
+    # when someparam.unit is configured, this differs from finalunit
+    assert m.parameters['someparam'].datatype.unit == someunit