diff --git a/python/plugins/processing/gui/AlgorithmDialog.py b/python/plugins/processing/gui/AlgorithmDialog.py
index 2107b1f50af..38b88d1c80e 100644
--- a/python/plugins/processing/gui/AlgorithmDialog.py
+++ b/python/plugins/processing/gui/AlgorithmDialog.py
@@ -104,6 +104,10 @@ class AlgorithmDialog(QgsProcessingAlgorithmDialogBase):
                 except KeyError:
                     continue
 
+                # For compatibility with 3.x API, we need to check whether the wrapper is
+                # the deprecated WidgetWrapper class. If not, it's the newer
+                # QgsAbstractProcessingParameterWidgetWrapper class
+                # TODO QGIS 4.0 - remove
                 if issubclass(wrapper.__class__, WidgetWrapper):
                     widget = wrapper.widget
                 else:
diff --git a/python/plugins/processing/gui/BatchPanel.py b/python/plugins/processing/gui/BatchPanel.py
index 9431ec84ae7..f8dcd11c1da 100644
--- a/python/plugins/processing/gui/BatchPanel.py
+++ b/python/plugins/processing/gui/BatchPanel.py
@@ -234,6 +234,10 @@ class BatchPanel(BASE, WIDGET):
     def setCellWrapper(self, row, column, wrapper, context):
         self.wrappers[row][column] = wrapper
 
+        # For compatibility with 3.x API, we need to check whether the wrapper is
+        # the deprecated WidgetWrapper class. If not, it's the newer
+        # QgsAbstractProcessingParameterWidgetWrapper class
+        # TODO QGIS 4.0 - remove
         is_cpp_wrapper = not issubclass(wrapper.__class__, WidgetWrapper)
         if is_cpp_wrapper:
             widget = wrapper.createWrappedWidget(context)
diff --git a/python/plugins/processing/gui/ParametersPanel.py b/python/plugins/processing/gui/ParametersPanel.py
index 759dae79ff8..7dc38110851 100644
--- a/python/plugins/processing/gui/ParametersPanel.py
+++ b/python/plugins/processing/gui/ParametersPanel.py
@@ -131,6 +131,11 @@ class ParametersPanel(BASE, WIDGET):
             else:
                 wrapper = WidgetWrapperFactory.create_wrapper(param, self.parent)
                 self.wrappers[param.name()] = wrapper
+
+                # For compatibility with 3.x API, we need to check whether the wrapper is
+                # the deprecated WidgetWrapper class. If not, it's the newer
+                # QgsAbstractProcessingParameterWidgetWrapper class
+                # TODO QGIS 4.0 - remove
                 is_python_wrapper = issubclass(wrapper.__class__, WidgetWrapper)
                 if not is_python_wrapper:
                     widget = wrapper.createWrappedWidget(self.processing_context)