--- a/parser/expat/lib/xmlparse.c
+++ b/parser/expat/lib/xmlparse.c
@@ -21,17 +21,19 @@
 #include "expat.h"
 
 #ifdef XML_UNICODE
 #define XML_ENCODE_MAX XML_UTF16_ENCODE_MAX
 #define XmlConvert XmlUtf16Convert
 #define XmlGetInternalEncoding XmlGetUtf16InternalEncoding
 #define XmlGetInternalEncodingNS XmlGetUtf16InternalEncodingNS
 #define XmlEncode XmlUtf16Encode
-#define MUST_CONVERT(enc, s) (!(enc)->isUtf16 || (((unsigned long)s) & 1))
+
+/* Using pointer subtraction to convert to integer type. */
+#define MUST_CONVERT(enc, s) (!(enc)->isUtf16 || (((char *)(s) - (char *)NULL) & 1))
 typedef unsigned short ICHAR;
 #else
 #define XML_ENCODE_MAX XML_UTF8_ENCODE_MAX
 #define XmlConvert XmlUtf8Convert
 #define XmlGetInternalEncoding XmlGetUtf8InternalEncoding
 #define XmlGetInternalEncodingNS XmlGetUtf8InternalEncodingNS
 #define XmlEncode XmlUtf8Encode
 #define MUST_CONVERT(enc, s) (!(enc)->isUtf8)