diff --git a/FlatCAMObj.py b/FlatCAMObj.py
index 2574232b..6029ca31 100644
--- a/FlatCAMObj.py
+++ b/FlatCAMObj.py
@@ -981,6 +981,9 @@ class FlatCAMGerber(FlatCAMObj, Gerber):
 
         def geo_init(geo_obj, app_obj):
             assert isinstance(geo_obj, FlatCAMGeometry)
+            if isinstance(self.solid_geometry, list):
+                self.solid_geometry = cascaded_union(self.solid_geometry)
+
             bounding_box = self.solid_geometry.envelope.buffer(float(self.options["noncoppermargin"]))
             if not self.options["noncopperrounded"]:
                 bounding_box = bounding_box.envelope
diff --git a/README.md b/README.md
index fdd73dba..263a30fc 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,10 @@ CAD program, and create G-Code for Isolation routing.
 
 =================================================
 
+20.12.2019
+
+- fixed a rare issue in the generation of non-copper-region geometry started from the Gerber Object UI (selected tab)
+
 19.12.2019
 
 - in 2-Sided Tool added a way to calculate the bounding box values for a selection of objects, and also the centroid