diff --git a/src/channel.c b/src/channel.c
index 3a80748..b013a85 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -80,24 +80,34 @@
     static int
 fd_write(sock_T fd, char *buf, size_t len)
 {
+    size_t	todo = len;
     HANDLE	h = (HANDLE)fd;
-    DWORD	nwrite;
+    DWORD	nwrite, size, done = 0;
     OVERLAPPED	ov;
 
-    // If the pipe overflows while the job does not read the data, WriteFile
-    // will block forever. This abandons the write.
-    memset(&ov, 0, sizeof(ov));
-    if (!WriteFile(h, buf, (DWORD)len, &nwrite, &ov))
+    while (todo > 0)
     {
-	DWORD err = GetLastError();
+	if (todo > MAX_NAMED_PIPE_SIZE)
+	    size = MAX_NAMED_PIPE_SIZE;
+	else
+	    size = todo;
+	// If the pipe overflows while the job does not read the data, WriteFile
+	// will block forever. This abandons the write.
+	memset(&ov, 0, sizeof(ov));
+	if (!WriteFile(h, buf + done, size, &nwrite, &ov))
+	{
+	    DWORD err = GetLastError();
 
-	if (err != ERROR_IO_PENDING)
-	    return -1;
-	if (!GetOverlappedResult(h, &ov, &nwrite, FALSE))
-	    return -1;
-	FlushFileBuffers(h);
+	    if (err != ERROR_IO_PENDING)
+		return -1;
+	    if (!GetOverlappedResult(h, &ov, &nwrite, FALSE))
+		return -1;
+	    FlushFileBuffers(h);
+	}
+	todo -= nwrite;
+	done += nwrite;
     }
-    return (int)nwrite;
+    return (int)done;
 }
 
     static void
diff --git a/src/os_win32.c b/src/os_win32.c
index 8966053..6a127a4 100644
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -5369,7 +5369,7 @@
 	    name,
 	    PIPE_ACCESS_OUTBOUND | FILE_FLAG_OVERLAPPED,
 	    PIPE_TYPE_BYTE | PIPE_NOWAIT,
-	    1, 65535, 0, 0, NULL);
+	    1, MAX_NAMED_PIPE_SIZE, 0, 0, NULL);
 
     if (handles[1] == INVALID_HANDLE_VALUE)
 	return FALSE;
diff --git a/src/testdir/test_channel.vim b/src/testdir/test_channel.vim
index 15ca9dd..e7fcf95 100644
--- a/src/testdir/test_channel.vim
+++ b/src/testdir/test_channel.vim
@@ -1980,3 +1980,21 @@
   unlet! g:val
   unlet! g:job
 endfunc
+
+func Test_raw_large_data()
+  try
+    let g:out = ''
+    let job = job_start(s:python . " test_channel_pipe.py",
+	  \ {'mode': 'raw', 'drop': 'never', 'noblock': 1,
+      \  'callback': {ch, msg -> execute('let g:out .= msg')}})
+
+    let want = repeat('X', 79999) . "\n"
+    call ch_sendraw(job, want)
+    let g:Ch_job = job
+    call WaitForAssert({-> assert_equal("dead", job_status(g:Ch_job))})
+    call assert_equal(want, substitute(g:out, '\r', '', 'g'))
+  finally
+    call job_stop(job)
+    unlet g:out
+  endtry
+endfunc
diff --git a/src/testdir/test_channel_pipe.py b/src/testdir/test_channel_pipe.py
index 9403786..810a8e3 100644
--- a/src/testdir/test_channel_pipe.py
+++ b/src/testdir/test_channel_pipe.py
@@ -56,4 +56,8 @@
         if typed.startswith("doubleerr "):
             print(typed[10:-1] + "\nAND " + typed[10:-1], file=sys.stderr)
             sys.stderr.flush()
+        if typed.startswith("XXX"):
+            print(typed, end='')
+            sys.stderr.flush()
+            break
 
diff --git a/src/version.c b/src/version.c
index 532b449..4beae27 100644
--- a/src/version.c
+++ b/src/version.c
@@ -788,6 +788,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    818,
+/**/
     817,
 /**/
     816,
diff --git a/src/vim.h b/src/vim.h
index 55cb693..5bd1b3c 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2467,6 +2467,10 @@
 # define MAX_OPEN_CHANNELS 0
 #endif
 
+#if defined(WIN32)
+# define MAX_NAMED_PIPE_SIZE 65535
+#endif
+
 /* Options for json_encode() and json_decode. */
 #define JSON_JS		1   /* use JS instead of JSON */
 #define JSON_NO_NONE	2   /* v:none item not allowed */