diff --git a/src/Mod/Fem/SelectionObserverFem.py b/src/Mod/Fem/SelectionObserverFem.py
index c0cc4013b..39a192e91 100644
--- a/src/Mod/Fem/SelectionObserverFem.py
+++ b/src/Mod/Fem/SelectionObserverFem.py
@@ -39,6 +39,5 @@ class SelectionObserverFem:
     def addSelection(self, docName, objName, sub, pos):
         selected_object = FreeCAD.getDocument(docName).getObject(objName)  # get the obj objName
         self.added_obj = (selected_object, sub)
-
-        if sub:         # on doubleClick the solid is selected and sub will be empty
-            self.parseSelectionFunction(self.added_obj)
+        # on double click on a vertex of a solid sub is None and obj is the solid
+        self.parseSelectionFunction(self.added_obj)
diff --git a/src/Mod/Fem/_TaskPanelFemBeamSection.py b/src/Mod/Fem/_TaskPanelFemBeamSection.py
index 403e689c0..db0496396 100644
--- a/src/Mod/Fem/_TaskPanelFemBeamSection.py
+++ b/src/Mod/Fem/_TaskPanelFemBeamSection.py
@@ -93,15 +93,14 @@ class _TaskPanelFemBeamSection:
     def selectionParser(self, selection):
         # print('selection: ', selection[0].Shape.ShapeType, '  ', selection[0].Name, '  ', selection[1])
         if hasattr(selection[0], "Shape"):
-            elt = selection[0].Shape.getElement(selection[1])
-            if elt.ShapeType == 'Edge':
-                if selection not in self.references:
-                    self.references.append(selection)
-                    self.rebuild_list_References()
-                else:
-                    print(selection[0].Name, '-->', selection[1], ' is already in reference list!')
-        else:
-            print('Selection has no shape!')
+            if selection[1]:
+                elt = selection[0].Shape.getElement(selection[1])
+                if elt.ShapeType == 'Edge':
+                    if selection not in self.references:
+                        self.references.append(selection)
+                        self.rebuild_list_References()
+                    else:
+                        print(selection[0].Name, '-->', selection[1], ' is already in reference list!')
 
     def rebuild_list_References(self):
         self.form.list_References.clear()
diff --git a/src/Mod/Fem/_TaskPanelFemShellThickness.py b/src/Mod/Fem/_TaskPanelFemShellThickness.py
index 10da5c642..764596a76 100644
--- a/src/Mod/Fem/_TaskPanelFemShellThickness.py
+++ b/src/Mod/Fem/_TaskPanelFemShellThickness.py
@@ -93,15 +93,14 @@ class _TaskPanelFemShellThickness:
     def selectionParser(self, selection):
         # print('selection: ', selection[0].Shape.ShapeType, '  ', selection[0].Name, '  ', selection[1])
         if hasattr(selection[0], "Shape"):
-            elt = selection[0].Shape.getElement(selection[1])
-            if elt.ShapeType == 'Face':
-                if selection not in self.references:
-                    self.references.append(selection)
-                    self.rebuild_list_References()
-                else:
-                    print(selection[0].Name, '-->', selection[1], ' is already in reference list!')
-        else:
-            print('Selection has no shape!')
+            if selection[1]:
+                elt = selection[0].Shape.getElement(selection[1])
+                if elt.ShapeType == 'Face':
+                    if selection not in self.references:
+                        self.references.append(selection)
+                        self.rebuild_list_References()
+                    else:
+                        print(selection[0].Name, '-->', selection[1], ' is already in reference list!')
 
     def rebuild_list_References(self):
         self.form.list_References.clear()
diff --git a/src/Mod/Fem/_TaskPanelMechanicalMaterial.py b/src/Mod/Fem/_TaskPanelMechanicalMaterial.py
index b5418ac53..7e2e4ecae 100644
--- a/src/Mod/Fem/_TaskPanelMechanicalMaterial.py
+++ b/src/Mod/Fem/_TaskPanelMechanicalMaterial.py
@@ -241,7 +241,10 @@ class _TaskPanelMechanicalMaterial:
         # here the addReference button EditTaskPanel has to be triggered to start selection mode
         FreeCADGui.Selection.clearSelection()
         # start SelectionObserver and parse the function to add the References to the widget
-        self.sel_server = ReferenceShapeSelectionObserver(self.selectionParser)
+        # TODO add a ToolTip with print_message if the mouse pointer is over addReference button
+        print_message = "Select Edges and Faces by single click on them or Solids by double click on a Vertex to add them to the list"
+        import SelectionObserverFem
+        self.sel_server = SelectionObserverFem.SelectionObserverFem(self.selectionParser, print_message)
 
     def selectionParser(self, selection):
         # print('selection: ', selection[0].Shape.ShapeType, '  ', selection[0].Name, '  ', selection[1])
@@ -261,10 +264,6 @@ class _TaskPanelMechanicalMaterial:
                         FreeCAD.Console.PrintMessage(selection[0].Name + ' --> ' + selection[1] + ' is in reference list already!\n')
                 else:
                     FreeCAD.Console.PrintMessage(elt.ShapeType + ' selected, but reference list has ' + self.references_shape_type + 's already!\n')
-            else:
-                FreeCAD.Console.PrintMessage("Select Edges and Faces by single click on them or Solids by double click on a Vertex!\n")
-        else:
-            FreeCAD.Console.PrintMessage("Selection has no shape!\n")
 
     def rebuild_list_References(self):
         self.form.list_References.clear()
@@ -277,19 +276,3 @@ class _TaskPanelMechanicalMaterial:
             items.append(item_name)
         for listItemName in sorted(items):
             self.form.list_References.addItem(listItemName)
-
-
-class ReferenceShapeSelectionObserver:
-    '''ReferenceShapeSelectionObserver
-       started on click  button addReference'''
-    def __init__(self, parseSelectionFunction):
-        self.parseSelectionFunction = parseSelectionFunction
-        FreeCADGui.Selection.addObserver(self)
-        FreeCAD.Console.PrintMessage("Select Edges and Faces by single click on them or Solids by double click on a Vertex!\n")
-        # TODO add a ToolTip if mouse pointer is over addReference button
-
-    def addSelection(self, docName, objName, sub, pos):
-        selected_object = FreeCAD.getDocument(docName).getObject(objName)  # get the obj objName
-        self.added_obj = (selected_object, sub)
-        # on double click on a vertex of a solid sub is None and obj is the solid
-        self.parseSelectionFunction(self.added_obj)