diff --git a/gns3server/compute/dynamips/nodes/ethernet_switch.py b/gns3server/compute/dynamips/nodes/ethernet_switch.py
index 594b3cb5..9f66b4d2 100644
--- a/gns3server/compute/dynamips/nodes/ethernet_switch.py
+++ b/gns3server/compute/dynamips/nodes/ethernet_switch.py
@@ -87,6 +87,7 @@ class EthernetSwitch(Device):
         self._mappings = {}
         self._telnet_console = None
         self._telnet_shell = None
+        self._telnet_server = None
         self._console = self._manager.port_manager.get_free_tcp_port(self._project)
         if ports is None:
             # create 8 ports by default
@@ -217,8 +218,9 @@ class EthernetSwitch(Device):
         Deletes this Ethernet switch.
         """
         yield from self._telnet.close()
-        self._telnet_server.close()
-        
+        if self._telnet_server:
+            self._telnet_server.close()
+
         for nio in self._nios.values():
             if nio:
                 yield from nio.close()
diff --git a/setup.py b/setup.py
index 02663755..46f9b2cb 100644
--- a/setup.py
+++ b/setup.py
@@ -62,17 +62,21 @@ setup(
     zip_safe=False,
     platforms="any",
     classifiers=[
-        "Development Status :: 4 - Beta",
+        "Development Status :: 5 - Production/Stable",
         "Environment :: Console",
         "Intended Audience :: Information Technology",
         "Topic :: System :: Networking",
         "License :: OSI Approved :: GNU General Public License v3 (GPLv3)",
         "Natural Language :: English",
-        "Operating System :: OS Independent",
+        "Operating System :: POSIX",
+        "Operating System :: MacOS :: MacOS X",
+        "Operating System :: Microsoft :: Windows",
         "Programming Language :: Python",
         "Programming Language :: Python :: 3",
         "Programming Language :: Python :: 3.4",
         "Programming Language :: Python :: 3.5",
+        "Programming Language :: Python :: 3.6",
+        "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: Implementation :: CPython",
     ],
 )