diff --git a/libevent/event_iocp.c b/libevent/event_iocp.c
index 4c144af..0e0586e 100644
--- a/libevent/event_iocp.c
+++ b/libevent/event_iocp.c
@@ -28,6 +28,7 @@
 #include <windows.h>
 #include <process.h>
 #include <stdio.h>
+#include <mswsock.h>
 
 #include "event2/util.h"
 #include "util-internal.h"
@@ -98,6 +99,34 @@ event_iocp_port_associate(struct event_iocp_port *port, evutil_socket_t fd,
 	return 0;
 }
 
+static void *
+get_extention_function(SOCKET s, GUID which_fn)
+{
+	void *ptr = NULL;
+	DWORD bytes;
+	WSAIoctl(s, SIO_GET_EXTENSION_FUNCTION_POINER,
+	    &which_fn, sizeof(which_fn),
+	    &ptr, sizeof(ptr),
+	    NULL, NULL);
+
+	/* No need to detect errors here: if ptr is set, then we have a good
+	   function pointer.  Otherwise, we should behave as if we had no
+	   function pointer.
+	*/
+	return ptr;
+}
+
+static void
+init_extension_functions(struct win32_extension_fns *ext)
+{
+	SOCKET s = socket(AF_INET, SOCK_STREAM, 0);
+	if (s < 0)
+		return;
+	ext->AcceptEx = get_extension_function(s, WSAID_ACCEPTEX);
+	ext->ConnectEx = get_extension_function(s, WSAID_CONNECTEX);
+	closesocket(s);
+}
+
 struct event_iocp_port *
 event_iocp_port_launch(void)
 {
@@ -130,6 +159,8 @@ event_iocp_port_launch(void)
 
 	InitializeCriticalSection(&port->lock);
 
+	init_extension_functions(&port->ext);
+
 	return port;
 err:
 	if (port->port)
diff --git a/libevent/iocp-internal.h b/libevent/iocp-internal.h
index d743bd5..414066a 100644
--- a/libevent/iocp-internal.h
+++ b/libevent/iocp-internal.h
@@ -53,6 +53,14 @@ struct event_overlapped {
 	iocp_callback cb;
 };
 
+/** Internal use only. Holds pointers to functions that only some versions of
+    Windows provide.
+ */
+struct win32_extention_fns {
+	LPFN_ACCEPTEX AcceptEx;
+	LPFN_CONNECTEX ConnectEx;
+};
+
 /**
     Internal use only. Stores a Windows IO Completion port, along with
     related data.
@@ -73,8 +81,10 @@ struct event_iocp_port {
 	HANDLE *threads;
 	/** Number of threads currently open on this port. */
 	short n_live_threads;
-	/* A semaphore to signal when we are done shutting down. */
+	/** A semaphore to signal when we are done shutting down. */
 	HANDLE *shutdownSemaphore;
+	/** Function pointers that only some versions of windows provide. */
+	struct win32_extension_fns ext;
 };
 #else
 /* Dummy definition so we can test-compile more things on unix. */