diff --git a/varlink/server.py b/varlink/server.py
index 03e7259..8031cd5 100644
--- a/varlink/server.py
+++ b/varlink/server.py
@@ -3,7 +3,6 @@
 import os
 import socket
 import stat
-import string
 from socketserver import BaseServer, StreamRequestHandler, ThreadingMixIn
 
 from .error import InterfaceNotFound, InvalidParameter, MethodNotImplemented, VarlinkEncoder, VarlinkError
@@ -138,23 +137,16 @@ def _handle(self, message, raw_message, _server=None, _request=None):
 
             kwargs = {}
 
-            if hasattr(inspect, "signature"):
-                sig = inspect.signature(func)
-                arg_names = [
-                    (
-                        sig.parameters[k].kind
-                        in (inspect.Parameter.POSITIONAL_OR_KEYWORD, inspect.Parameter.KEYWORD_ONLY)
-                        and k
-                        or None
-                    )
-                    for k in sig.parameters.keys()
-                ]
-            else:
-                from itertools import izip
-
-                spec = inspect.getargspec(func)
-                matched_args = [reversed(x) for x in [spec.args, spec.defaults or []]]
-                arg_names = dict(izip(*matched_args))
+            sig = inspect.signature(func)
+            arg_names = [
+                (
+                    sig.parameters[k].kind
+                    in (inspect.Parameter.POSITIONAL_OR_KEYWORD, inspect.Parameter.KEYWORD_ONLY)
+                    and k
+                    or None
+                )
+                for k in sig.parameters.keys()
+            ]
 
             if message.get("more", False) or message.get("oneway", False) or message.get("upgrade", False):
                 if message.get("more", False) and "_more" in arg_names:
@@ -312,7 +304,7 @@ def get_listen_fd():
         except OSError:
             return None
 
-    fields = string.split(os.environ["LISTEN_FDNAMES"], ":")
+    fields = os.environ.get("LISTEN_FDNAMES", "").split(":")
 
     if len(fields) != fds:
         return None