diff --git a/lib/drawdxf.py b/lib/drawdxf.py
index a623a8b..c28ea4b 100644
--- a/lib/drawdxf.py
+++ b/lib/drawdxf.py
@@ -78,6 +78,7 @@ def new_dxf(plines, out_path):
     """ creates a new dxf file with a polyline inside which is created by the given json file
     """
     doc = ezdxf.new('R2018', setup=True)
+    doc.header['$INSUNITS'] = 4  # Millimeter
     draw_cables(plines, doc)
     draw_sensors(plines, doc)
     draw_subdists(plines, doc)