diff --git a/README.md b/README.md
index 3ea0b7a38063a820eb85fb7fe5ad86b2fdfa2999..31d9efbacd25604111d6bff540a51c9e84704ac8 100644
--- a/README.md
+++ b/README.md
@@ -34,6 +34,7 @@ LICENSE: LGPL - see LICENSE file
 
 CHANGELOG:
 
+1.7.1   - Enable support for optional fields
 1.7.0   - Optional fields and fix segfaults when updating CHOICE fields
 1.6.9   - Add basic support for optional fields
 1.6.7   - Fix CPU usage of polling thread
diff --git a/asn1_value_editor/asn1_value_editor.py b/asn1_value_editor/asn1_value_editor.py
index 1bb2043eeac057781a482e8a7da63ea0beadb32b..f059a84eddde7d4523566172c200607469187e67 100755
--- a/asn1_value_editor/asn1_value_editor.py
+++ b/asn1_value_editor/asn1_value_editor.py
@@ -16,7 +16,7 @@
 
 __author__ = "Maxime Perrotin"
 __license__ = "LGPLv3"
-__version__ = "1.7.0"
+__version__ = "1.7.1"
 __url__ = "https://taste.tools"
 
 import sys
@@ -420,7 +420,7 @@ class asn1Editor(QTreeView):
                     dest.Reset(stateBefore)
                     # Check if field is optional and set the .exist.field
                     # accordingly
-                    field_root = root.child(i)
+                    #field_root = root.child(i)
                     field_name = \
                             root.child(i, 0).text().replace('-', '_')
                     field_optionality = root.child(i, 4)
@@ -428,10 +428,10 @@ class asn1Editor(QTreeView):
                             and field_optionality.isCheckable():
                         present = field_optionality.checkState() == Qt.Checked
                         print field_name, "SET" if present else "UNSET"
-                        # Uncomment the following when Stubs.py supports it:
-                        #ptr = getattr(dest, "exist")
-                        #ptr = getattr(ptr, field_name)
-                        #ptr.Set (1 if present else 0)
+                        # Set the "exist" value for optional fields
+                        ptr = getattr(dest, "exist")
+                        ptr = getattr(ptr, field_name)
+                        ptr.Set (1 if present else 0)
                         dest.Reset(stateBefore)
 
 
@@ -574,6 +574,22 @@ class asn1Editor(QTreeView):
                     fillRow(root, i, ptr, seqOf=seqOf)
                     ptr.Reset(stateBefore)
 
+                    # check if field is optional and set checkbox from value
+                    field_name = \
+                            root.child(i, 0).text().replace('-', '_')
+                    field_optionality = root.child(i, 4)
+                    if field_optionality.data(OPTIONAL) \
+                            and field_optionality.isCheckable():
+                        # Set the "exist" value for optional fields
+                        ptr = getattr(ptr, "exist")
+                        ptr = getattr(ptr, field_name)
+                        present = ptr.Get()
+                        print field_name, field_optionality.data(OPTIONAL), present
+                        field_optionality.setCheckState (Qt.Checked if present
+                                                    else Qt.Unchecked)
+                        ptr.Reset(stateBefore)
+
+
     def updateVariable(self, root=None, asn1Var=None):
         ''' Update the variable value (when loading a TC or receiving a TM) '''
         root         = root or self.treeItem