Use a buffer large enough to ensure we don't overrun, even if the value
is outside the range we expect.
diff --git a/Modules/datetimemodule.c b/Modules/datetimemodule.c
index 89423ab..3f9e78b 100644
--- a/Modules/datetimemodule.c
+++ b/Modules/datetimemodule.c
@@ -1133,7 +1133,7 @@
 static PyObject *
 make_freplacement(PyObject *object)
 {
-	char freplacement[7];
+	char freplacement[64];
 	if (PyTime_Check(object))
 	    sprintf(freplacement, "%06d", TIME_GET_MICROSECOND(object));
 	else if (PyDateTime_Check(object))