Fix MSVC compiler warning
diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
index b56b66a..7e6e9b3 100644
--- a/expat/lib/xmlparse.c
+++ b/expat/lib/xmlparse.c
@@ -728,7 +728,7 @@
   if (sizeof(unsigned long) == 4) {
     return entropy * 2147483647;
   } else {
-    return entropy * 2305843009213693951;
+    return entropy * (unsigned long)2305843009213693951;
   }
 }