diff --git a/Lib/ctypes/test/test_loading.py b/Lib/ctypes/test/test_loading.py
index 1e7870b..18dcdbf 100644
--- a/Lib/ctypes/test/test_loading.py
+++ b/Lib/ctypes/test/test_loading.py
@@ -74,5 +74,33 @@
 
             self.failUnlessRaises(AttributeError, dll.__getitem__, 1234)
 
+    if os.name == "nt":
+        def test_1703286_A(self):
+            from _ctypes import LoadLibrary, FreeLibrary
+            # On winXP 64-bit, advapi32 loads at an address that does
+            # NOT fit into a 32-bit integer.  FreeLibrary must be able
+            # to accept this address.
+
+            # These are tests for http://www.python.org/sf/1703286
+            handle = LoadLibrary("advapi32")
+            FreeLibrary(handle)
+
+        def test_1703286_B(self):
+            # Since on winXP 64-bit advapi32 loads like described
+            # above, the (arbitrarily selected) CloseEventLog function
+            # also has a high address.  'call_function' should accept
+            # addresses so large.
+            from _ctypes import call_function
+            advapi32 = windll.advapi32
+            # Calling CloseEventLog with a NULL argument should fail,
+            # but the call should not segfault or so.
+            self.failUnlessEqual(0, advapi32.CloseEventLog(None))
+            windll.kernel32.GetProcAddress.argtypes = c_void_p, c_char_p
+            windll.kernel32.GetProcAddress.restype = c_void_p
+            proc = windll.kernel32.GetProcAddress(advapi32._handle, "CloseEventLog")
+            self.failUnless(proc)
+            # This is the real test: call the function via 'call_function'
+            self.failUnlessEqual(0, call_function(proc, (None,)))
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/Misc/NEWS b/Misc/NEWS
index 136ab5c..4f9d648 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -54,6 +54,8 @@
 Extension Modules
 -----------------
 
+- Bug #1703286: ctypes no longer truncates 64-bit pointers.
+
 - Bug #1721309: prevent bsddb module from freeing random memory.
 
 - Bug #1726026: Correct the field names of WIN32_FIND_DATAA and
diff --git a/Modules/_ctypes/callproc.c b/Modules/_ctypes/callproc.c
index 0c35f38..58aa9bb 100644
--- a/Modules/_ctypes/callproc.c
+++ b/Modules/_ctypes/callproc.c
@@ -1111,10 +1111,10 @@
 Free the handle of an executable previously loaded by LoadLibrary.\n";
 static PyObject *free_library(PyObject *self, PyObject *args)
 {
-	HMODULE hMod;
-	if (!PyArg_ParseTuple(args, "i:FreeLibrary", &hMod))
+	void *hMod;
+	if (!PyArg_ParseTuple(args, PY_VOID_P_CODE ":FreeLibrary", &hMod))
 		return NULL;
-	if (!FreeLibrary(hMod))
+	if (!FreeLibrary((HMODULE)hMod))
 		return PyErr_SetFromWindowsErr(GetLastError());
 	Py_INCREF(Py_None);
 	return Py_None;
@@ -1233,9 +1233,9 @@
 
 static PyObject *py_dl_close(PyObject *self, PyObject *args)
 {
-	void * handle;
+	void *handle;
 
-	if (!PyArg_ParseTuple(args, "i:dlclose", &handle))
+	if (!PyArg_ParseTuple(args, PY_VOID_P_CODE ":dlclose", &handle))
 		return NULL;
 	if (dlclose(handle)) {
 		PyErr_SetString(PyExc_OSError,
@@ -1252,7 +1252,7 @@
 	void *handle;
 	void *ptr;
 
-	if (!PyArg_ParseTuple(args, "is:dlsym", &handle, &name))
+	if (!PyArg_ParseTuple(args, PY_VOID_P_CODE "s:dlsym", &handle, &name))
 		return NULL;
 	ptr = ctypes_dlsym(handle, name);
 	if (!ptr) {
@@ -1260,7 +1260,7 @@
 				       ctypes_dlerror());
 		return NULL;
 	}
-	return Py_BuildValue("i", ptr);
+	return PyLong_FromVoidPtr(ptr);
 }
 #endif
 
@@ -1272,12 +1272,12 @@
 static PyObject *
 call_function(PyObject *self, PyObject *args)
 {
-	PPROC func;
+	void *func;
 	PyObject *arguments;
 	PyObject *result;
 
 	if (!PyArg_ParseTuple(args,
-			      "iO!",
+			      PY_VOID_P_CODE "O!",
 			      &func,
 			      &PyTuple_Type, &arguments))
 		return NULL;
@@ -1303,12 +1303,12 @@
 static PyObject *
 call_cdeclfunction(PyObject *self, PyObject *args)
 {
-	PPROC func;
+	void *func;
 	PyObject *arguments;
 	PyObject *result;
 
 	if (!PyArg_ParseTuple(args,
-			      "iO!",
+			      PY_VOID_P_CODE "O!",
 			      &func,
 			      &PyTuple_Type, &arguments))
 		return NULL;
diff --git a/Modules/_ctypes/ctypes.h b/Modules/_ctypes/ctypes.h
index 0af7851..5fb6030 100644
--- a/Modules/_ctypes/ctypes.h
+++ b/Modules/_ctypes/ctypes.h
@@ -23,6 +23,12 @@
 #define PY_LONG_LONG LONG_LONG
 #endif
 
+#if SIZEOF_VOID_P == SIZEOF_LONG
+#define PY_VOID_P_CODE "k"
+#elif defined(HAVE_LONG_LONG) && (SIZEOF_VOID_P == SIZEOF_LONG_LONG)
+#define PY_VOID_P_CODE "K"
+#endif
+
 typedef struct tagPyCArgObject PyCArgObject;
 typedef struct tagCDataObject CDataObject;
 typedef PyObject *(* GETFUNC)(void *, unsigned size);