diff --git a/FlatCAMObj.py b/FlatCAMObj.py
index 2785cd2f..8dca424c 100644
--- a/FlatCAMObj.py
+++ b/FlatCAMObj.py
@@ -2353,7 +2353,7 @@ class FlatCAMExcellon(FlatCAMObj, Excellon):
 
             geo_obj.options['Tools_in_use'] = tool_table_items
             geo_obj.options['type'] = 'Excellon Geometry'
-            geo_obj.options["cnctooldia"] = float(tooldia)
+            geo_obj.options["cnctooldia"] = str(tooldia)
 
             geo_obj.solid_geometry = []
 
@@ -2448,7 +2448,7 @@ class FlatCAMExcellon(FlatCAMObj, Excellon):
 
             geo_obj.options['Tools_in_use'] = tool_table_items
             geo_obj.options['type'] = 'Excellon Geometry'
-            geo_obj.options["cnctooldia"] = float(tooldia)
+            geo_obj.options["cnctooldia"] = str(tooldia)
 
             geo_obj.solid_geometry = []
 
diff --git a/README.md b/README.md
index 7e32f10c..0a6b6b89 100644
--- a/README.md
+++ b/README.md
@@ -20,6 +20,7 @@ CAD program, and create G-Code for Isolation routing.
 - set the decimals for Grid values to be set to 6 if the units of FlatCAM is INCH and to set to 4 if FlatCAM units are METRIC
 - updated translations
 - updated the Russian translate from 51% complete to 69% complete using the Yandex translation engine
+- fixed recently introduced bug in milling drills/slots functions
 
 20.06.2019