diff -r 61a045ac0006 Lib/asyncio/subprocess.py
--- a/Lib/asyncio/subprocess.py	Thu Jan 15 00:05:18 2015 +0100
+++ b/Lib/asyncio/subprocess.py	Thu Jan 15 00:06:59 2015 +0100
@@ -107,6 +107,7 @@ class Process:
         self._transport = transport
         self._protocol = protocol
         self._loop = loop
+        self._returncode = None
         self.stdin = protocol.stdin
         self.stdout = protocol.stdout
         self.stderr = protocol.stderr
@@ -115,14 +116,25 @@ class Process:
     def __repr__(self):
         return '<%s %s>' % (self.__class__.__name__, self.pid)
 
+    def _get_returncode(self):
+        if self._returncode is not None:
+            return self._returncode
+        else:
+            returncode = self._transport.get_returncode()
+            if returncode is not None:
+                self._returncode = returncode
+                self._transport.close()
+                self._transport = None
+            return returncode
+
     @property
     def returncode(self):
-        return self._transport.get_returncode()
+        return self._get_returncode()
 
     @coroutine
     def wait(self):
         """Wait until the process exit and return the process return code."""
-        returncode = self._transport.get_returncode()
+        returncode = self._get_returncode()
         if returncode is not None:
             return returncode
 
@@ -132,7 +144,7 @@ class Process:
         return waiter.result()
 
     def _check_alive(self):
-        if self._transport.get_returncode() is not None:
+        if self._get_returncode() is not None:
             raise ProcessLookupError()
 
     def send_signal(self, signal):
@@ -189,6 +201,7 @@ class Process:
 
     @coroutine
     def communicate(self, input=None):
+        self._check_alive()
         if input:
             stdin = self._feed_stdin(input)
         else: