diff --git a/DevIL/src-IL/src/il_jp2.cpp b/DevIL/src-IL/src/il_jp2.cpp
index 89075a52..ba8317e3 100644
--- a/DevIL/src-IL/src/il_jp2.cpp
+++ b/DevIL/src-IL/src/il_jp2.cpp
@@ -324,22 +324,30 @@ ILboolean iLoadJp2Internal(jas_stream_t	*Stream, ILimage *Image)
 // see: https://github.com/OSGeo/gdal/commit/9ef8e16e27c5fc4c491debe50bf2b7f3e94ed334
 //      https://github.com/DentonW/DevIL/issues/90
 #if defined(PRIjas_seqent)
+#if JAS_VERSION_MAJOR >= 3
+static long int iJp2_file_read(jas_stream_obj_t *obj, char *buf, long unsigned int cnt)
+#elif JAS_VERSION_MAJOR < 3
 static int iJp2_file_read(jas_stream_obj_t *obj, char *buf, unsigned cnt)
 #else
 static int iJp2_file_read(jas_stream_obj_t *obj, char *buf, int cnt)
 #endif
+#endif
 {
 	obj;
 	return iread(buf, 1, cnt);
 }
 
 #if defined(JAS_INCLUDE_JP2_CODEC)
+#if JAS_VERSION_MAJOR >= 3
+static long int iJp2_file_write(jas_stream_obj_t *obj, const char *buf, long unsigned int cnt)
+#elif JAS_VERSION_MAJOR < 3
 static int iJp2_file_write(jas_stream_obj_t *obj, const char *buf, unsigned cnt)
 #elif defined(PRIjas_seqent)
 static int iJp2_file_write(jas_stream_obj_t *obj, char *buf, unsigned cnt)
 #else
 static int iJp2_file_write(jas_stream_obj_t *obj, char *buf, int cnt)
 #endif
+#endif
 {
 	obj;
 	return iwrite(buf, 1, cnt);