diff --git a/qasync/_windows.py b/qasync/_windows.py
index ec13ede..602044d 100644
--- a/qasync/_windows.py
+++ b/qasync/_windows.py
@@ -75,14 +75,56 @@ def close(self):
         self._logger.debug('Closing')
         super(_IocpProactor, self).close()
 
+    # Wrap all I/O submission methods to acquire the internal lock first; listed
+    # in the order they appear in the base class source code.
+
     def recv(self, conn, nbytes, flags=0):
         with QtCore.QMutexLocker(self._lock):
             return super(_IocpProactor, self).recv(conn, nbytes, flags)
 
+    def recv_into(self, conn, buf, flags=0):
+        with QtCore.QMutexLocker(self._lock):
+            return super(_IocpProactor, self).recv_into(conn, buf, flags)
+
+    def recvfrom(self, conn, nbytes, flags=0):
+        with QtCore.QMutexLocker(self._lock):
+            return super(_IocpProactor, self).recvfrom(conn, nbytes, flags)
+
+    def recvfrom_into(self, conn, buf, flags=0):
+        with QtCore.QMutexLocker(self._lock):
+            return super(_IocpProactor, self).recvfrom_into(conn, buf, flags)
+
+    def sendto(self, conn, buf, flags=0, addr=None):
+        with QtCore.QMutexLocker(self._lock):
+            return super(_IocpProactor, self).sendto(conn, buf, flags, addr)
+
     def send(self, conn, buf, flags=0):
         with QtCore.QMutexLocker(self._lock):
             return super(_IocpProactor, self).send(conn, buf, flags)
 
+    def accept(self, listener):
+        with QtCore.QMutexLocker(self._lock):
+            return super(_IocpProactor, self).accept(listener)
+
+    def connect(self, conn, address):
+        with QtCore.QMutexLocker(self._lock):
+            return super(_IocpProactor, self).connect(conn, address)
+
+    def sendfile(self, sock, file, offset, count):
+        with QtCore.QMutexLocker(self._lock):
+            return super(_IocpProactor, self).sendfile(sock, file, offset, count)
+
+    def accept_pipe(self, pipe):
+        with QtCore.QMutexLocker(self._lock):
+            return super(_IocpProactor, self).accept_pipe(pipe)
+
+    # connect_pipe() does not actually use the delayed completion machinery.
+
+    # This takes care of wait_for_handle() too.
+    def _wait_for_handle(self, handle, timeout, _is_cancel):
+        with QtCore.QMutexLocker(self._lock):
+            return super(_IocpProactor, self)._wait_for_handle(handle, timeout, _is_cancel)
+
     def _poll(self, timeout=None):
         """Override in order to handle events in a threadsafe manner."""
         if timeout is None:
@@ -123,18 +165,6 @@ def _poll(self, timeout=None):
 
                 ms = 0
 
-    def _wait_for_handle(self, handle, timeout, _is_cancel):
-        with QtCore.QMutexLocker(self._lock):
-            return super(_IocpProactor, self)._wait_for_handle(handle, timeout, _is_cancel)
-
-    def accept(self, listener):
-        with QtCore.QMutexLocker(self._lock):
-            return super(_IocpProactor, self).accept(listener)
-
-    def connect(self, conn, address):
-        with QtCore.QMutexLocker(self._lock):
-            return super(_IocpProactor, self).connect(conn, address)
-
 
 @with_logger
 class _EventWorker(QtCore.QThread):