diff --git a/extensions/fablabchemnitz_paths2openscad.py b/extensions/fablabchemnitz_paths2openscad.py
index 295e6bbb..402345b4 100644
--- a/extensions/fablabchemnitz_paths2openscad.py
+++ b/extensions/fablabchemnitz_paths2openscad.py
@@ -1368,7 +1368,9 @@ module chamfer_sphere(rad=chamfer, res=chamfer_fn)
                 **{"SCAD": scad_fname, "NAME": self.basename}
             )
             try:
-                m = re.match(r"(\d+)\s+(.*)", open(pidfile).read())
+                pfile=open(pidfile)
+                m = re.match(r"(\d+)\s+(.*)", pfile.read())
+                pfile.close()
                 oldpid = int(m.group(1))
                 oldcmd = m.group(2)
                 # print >> sys.stderr, "pid {1} seen in {0}".format(pidfile, oldpid)
@@ -1400,7 +1402,10 @@ module chamfer_sphere(rad=chamfer, res=chamfer_fn)
                 except OSError as e:
                     raise OSError("%s failed: errno=%d %s" % (cmd, e.errno, e.strerror))
                 try:
-                    open(pidfile, "w").write(str(proc.pid) + "\n" + cmd + "\n")
+                    pfile = open(pidfile, "w")
+                    pfile.write(str(proc.pid) + "\n" + cmd + "\n")
+                    pfile.close()
+                   
                 except Exception:
                     pass
             else:
@@ -1454,7 +1459,8 @@ module chamfer_sphere(rad=chamfer, res=chamfer_fn)
                 inkex.errormsg("= " * 24)
                 if len <= 0:  # something is wrong. better stop here
                     self.options.stlpost = "false"
-
+            stdout.close()
+            stderr.close()
             if self.options.stlpost == "true":
                 cmd = self.options.stlpostcmd.format(
                     **{"STL": self.basename + ".stl", "NAME": self.basename}
@@ -1481,5 +1487,7 @@ module chamfer_sphere(rad=chamfer, res=chamfer_fn)
                 if stderr:
                     inkex.errmsg("STDERR: {}".format(stderr))
                     inkex.errormsg("= " * 24)
+                    stdout.close()
+                    stderr.close()
 
-OpenSCAD().run()
\ No newline at end of file
+OpenSCAD().run()