diff --git a/CHANGELOG.md b/CHANGELOG.md
index fead9a47..1d090b70 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ CHANGELOG for FlatCAM beta
 
 =================================================
 
+23.10.2020
+
+- updated Copper Thieving Tool to work with the updated program
+
 22.10.2020
 
 - added  a message to show if voronoi_diagram method can be used (require Shapely >= 1.8)
diff --git a/appTools/ToolCopperThieving.py b/appTools/ToolCopperThieving.py
index 4a2f773f..2dae4151 100644
--- a/appTools/ToolCopperThieving.py
+++ b/appTools/ToolCopperThieving.py
@@ -519,9 +519,9 @@ class ToolCopperThieving(AppTool):
 
         ref_selected = self.ui.reference_radio.get_value()
         if c_val is None:
-            c_val = float(self.app.defaults["tools_copperfill_clearance"])
+            c_val = float(self.app.defaults["tools_copper_thieving_clearance"])
         if margin is None:
-            margin = float(self.app.defaults["tools_copperfill_margin"])
+            margin = float(self.app.defaults["tools_copper_thieving_margin"])
 
         fill_type = self.ui.fill_type_radio.get_value()
         dot_dia = self.ui.dot_dia_entry.get_value()
@@ -543,10 +543,8 @@ class ToolCopperThieving(AppTool):
             app_obj.app.inform.emit(_("Copper Thieving Tool. Preparing isolation polygons."))
 
             # variables to display the percentage of work done
-            geo_len = 0
             try:
-                for pol in app_obj.grb_object.solid_geometry:
-                    geo_len += 1
+                geo_len = len(app_obj.grb_object.solid_geometry)
             except TypeError:
                 geo_len = 1
 
@@ -613,10 +611,12 @@ class ToolCopperThieving(AppTool):
                         bounding_box = env_obj.buffer(distance=margin, join_style=base.JOIN_STYLE.mitre)
                     else:
                         if isinstance(geo_n, Polygon):
-                            bounding_box = geo_n.buffer(distance=margin, join_style=base.JOIN_STYLE.mitre).exterior
+                            bounding_box = geo_n.buffer(distance=margin, join_style=base.JOIN_STYLE.mitre)
                         elif isinstance(geo_n, list):
-                            geo_n = unary_union(geo_n)
-                            bounding_box = geo_n.buffer(distance=margin, join_style=base.JOIN_STYLE.mitre).exterior
+                            geo_n = MultiPolygon(geo_n)
+                            x0, y0, x1, y1 = geo_n.bounds
+                            geo = box(x0, y0, x1, y1)
+                            bounding_box = geo.buffer(distance=margin, join_style=base.JOIN_STYLE.mitre)
                         elif isinstance(geo_n, MultiPolygon):
                             x0, y0, x1, y1 = geo_n.bounds
                             geo = box(x0, y0, x1, y1)
@@ -689,10 +689,16 @@ class ToolCopperThieving(AppTool):
             # bounding_box = box(x0, y0, x1, y1)
             app_obj.app.proc_container.update_view_text(' %s' % _("Create geometry"))
 
-            bounding_box = thieving_obj.solid_geometry.envelope.buffer(
-                distance=margin,
-                join_style=base.JOIN_STYLE.mitre
-            )
+            try:
+                bounding_box = thieving_obj.solid_geometry.envelope.buffer(
+                    distance=margin,
+                    join_style=base.JOIN_STYLE.mitre
+                )
+            except AttributeError:
+                bounding_box = MultiPolygon(thieving_obj.solid_geometry).envelope.buffer(
+                    distance=margin,
+                    join_style=base.JOIN_STYLE.mitre
+                )
             x0, y0, x1, y1 = bounding_box.bounds
 
             if fill_type == 'dot' or fill_type == 'square':