Index: Modules/posixmodule.c
===================================================================
--- Modules/posixmodule.c	(revision 66863)
+++ Modules/posixmodule.c	(working copy)
@@ -2386,20 +2386,34 @@
 	/* assume encoded strings wont more than double no of chars */
 	char inbuf[MAX_PATH*2];
 	char *inbufp = inbuf;
-	Py_ssize_t insize = sizeof(inbuf);
-	char outbuf[MAX_PATH*2];
+	Py_ssize_t insize = sizeof(inbuf)/sizeof(inbuf[0]);
+	char outbuf[MAX_PATH+1];
 	char *temp;
+	PyObject *v;
+	DWORD result;
 #ifdef Py_WIN_WIDE_FILENAMES
 	if (unicode_file_names()) {
 		PyUnicodeObject *po;
 		if (PyArg_ParseTuple(args, "U|:_getfullpathname", &po)) {
+			Py_UNICODE *wpath = PyUnicode_AS_UNICODE(po);
 			Py_UNICODE woutbuf[MAX_PATH*2];
+			Py_UNICODE *woutbufp = woutbuf;
 			Py_UNICODE *wtemp;
-			if (!GetFullPathNameW(PyUnicode_AS_UNICODE(po),
-						sizeof(woutbuf)/sizeof(woutbuf[0]),
-						 woutbuf, &wtemp))
-				return win32_error("GetFullPathName", "");
-			return PyUnicode_FromUnicode(woutbuf, wcslen(woutbuf));
+			result = GetFullPathNameW(wpath, sizeof(woutbuf)/sizeof(woutbuf[0]),
+						   woutbuf, &wtemp);
+			if (result > sizeof(woutbuf)/sizeof(woutbuf[0])) {
+				woutbufp = malloc(result * sizeof(Py_UNICODE));
+				if (!woutbufp)
+					return PyErr_NoMemory();
+				result = GetFullPathNameW(wpath, result, woutbufp, &wtemp);
+			}
+			if (!result)
+				v = win32_error_unicode("GetFullPathName", wpath);
+			else
+				v = PyUnicode_FromUnicode(woutbufp, wcslen(woutbufp));
+			if (woutbufp != woutbuf)
+				free(woutbufp);
+			return v;
 		}
 		/* Drop the argument parsing error as narrow strings
 		   are also valid. */
@@ -2410,9 +2424,13 @@
 	                       Py_FileSystemDefaultEncoding, &inbufp,
 	                       &insize))
 		return NULL;
-	if (!GetFullPathName(inbuf, sizeof(outbuf)/sizeof(outbuf[0]),
-	                     outbuf, &temp))
+	result = GetFullPathNameA(inbuf, sizeof(outbuf)/sizeof(outbuf[0]),
+				  outbuf, &temp);
+	if (!result)
 		return win32_error("GetFullPathName", inbuf);
+	/* In the ANSI API, there should not be any paths longer
+	   than MAX_PATH. */
+	assert(result <= MAX_PATH+1);
 	if (PyUnicode_Check(PyTuple_GetItem(args, 0))) {
 		return PyUnicode_Decode(outbuf, strlen(outbuf),
 			Py_FileSystemDefaultEncoding, NULL);