diff --git a/Misc/NEWS.d/next/Library/2018-09-01-20-43-10.bpo-34563.7NQK7B.rst b/Misc/NEWS.d/next/Library/2018-09-01-20-43-10.bpo-34563.7NQK7B.rst
new file mode 100644
index 00000000000..9127af0d192
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-09-01-20-43-10.bpo-34563.7NQK7B.rst
@@ -0,0 +1 @@
+On Windows, fix multiprocessing.Connection for very large read: fix _winapi.PeekNamedPipe() and _winapi.ReadFile() for read larger than INT_MAX (usually 2^31-1).
\ No newline at end of file
diff --git a/Modules/_winapi.c b/Modules/_winapi.c
index c596cba3cbc..9ea5a926629 100644
--- a/Modules/_winapi.c
+++ b/Modules/_winapi.c
@@ -1337,7 +1337,7 @@ _winapi_PeekNamedPipe_impl(PyObject *module, HANDLE handle, int size)
         }
         if (_PyBytes_Resize(&buf, nread))
             return NULL;
-        return Py_BuildValue("Nii", buf, navail, nleft);
+        return Py_BuildValue("NII", buf, navail, nleft);
     }
     else {
         Py_BEGIN_ALLOW_THREADS
@@ -1346,7 +1346,7 @@ _winapi_PeekNamedPipe_impl(PyObject *module, HANDLE handle, int size)
         if (!ret) {
             return PyErr_SetExcFromWindowsErr(PyExc_OSError, 0);
         }
-        return Py_BuildValue("ii", navail, nleft);
+        return Py_BuildValue("II", navail, nleft);
     }
 }
 
@@ -1354,14 +1354,14 @@ _winapi_PeekNamedPipe_impl(PyObject *module, HANDLE handle, int size)
 _winapi.ReadFile
 
     handle: HANDLE
-    size: int
+    size: DWORD
     overlapped as use_overlapped: bool(accept={int}) = False
 [clinic start generated code]*/
 
 static PyObject *
-_winapi_ReadFile_impl(PyObject *module, HANDLE handle, int size,
+_winapi_ReadFile_impl(PyObject *module, HANDLE handle, DWORD size,
                       int use_overlapped)
-/*[clinic end generated code: output=492029ca98161d84 input=3f0fde92f74de59a]*/
+/*[clinic end generated code: output=d3d5b44a8201b944 input=08c439d03a11aac5]*/
 {
     DWORD nread;
     PyObject *buf;
diff --git a/Modules/clinic/_winapi.c.h b/Modules/clinic/_winapi.c.h
index b14f087732e..c66522ebab6 100644
--- a/Modules/clinic/_winapi.c.h
+++ b/Modules/clinic/_winapi.c.h
@@ -673,7 +673,7 @@ PyDoc_STRVAR(_winapi_ReadFile__doc__,
     {"ReadFile", (PyCFunction)_winapi_ReadFile, METH_FASTCALL|METH_KEYWORDS, _winapi_ReadFile__doc__},
 
 static PyObject *
-_winapi_ReadFile_impl(PyObject *module, HANDLE handle, int size,
+_winapi_ReadFile_impl(PyObject *module, HANDLE handle, DWORD size,
                       int use_overlapped);
 
 static PyObject *
@@ -681,9 +681,9 @@ _winapi_ReadFile(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyOb
 {
     PyObject *return_value = NULL;
     static const char * const _keywords[] = {"handle", "size", "overlapped", NULL};
-    static _PyArg_Parser _parser = {"" F_HANDLE "i|i:ReadFile", _keywords, 0};
+    static _PyArg_Parser _parser = {"" F_HANDLE "k|i:ReadFile", _keywords, 0};
     HANDLE handle;
-    int size;
+    DWORD size;
     int use_overlapped = 0;
 
     if (!_PyArg_ParseStackAndKeywords(args, nargs, kwnames, &_parser,
@@ -941,4 +941,4 @@ _winapi_GetFileType(PyObject *module, PyObject *const *args, Py_ssize_t nargs, P
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=ec7f36eb7efc9d00 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=baaf3d379b91be0a input=a9049054013a1b77]*/