--- a/id3tag.h
+++ b/id3tag.h
@@ -25,6 +25,8 @@
 # ifndef LIBID3TAG_ID3TAG_H
 # define LIBID3TAG_ID3TAG_H
 
+#include <stdint.h>
+
 # ifdef __cplusplus
 extern "C" {
 # endif
@@ -36,10 +38,10 @@
 typedef unsigned char id3_byte_t;
 typedef unsigned long id3_length_t;
 
-typedef unsigned long id3_ucs4_t;
+typedef uint32_t id3_ucs4_t;
 
 typedef unsigned char id3_latin1_t;
-typedef unsigned short id3_utf16_t;
+typedef uint16_t id3_utf16_t;
 typedef signed char id3_utf8_t;
 
 struct id3_tag {