diff --git a/frmts/jpeg2000/jpeg2000_vsil_io.cpp b/frmts/jpeg2000/jpeg2000_vsil_io.cpp
index 74f1e64..3a948d0 100644
--- a/frmts/jpeg2000/jpeg2000_vsil_io.cpp
+++ b/frmts/jpeg2000/jpeg2000_vsil_io.cpp
@@ -209,7 +209,7 @@ static void JPEG2000_VSIL_jas_stream_initbuf(jas_stream_t *stream, int bufmode,
 			/* The buffer must be large enough to accommodate maximum
 			  putback. */
 			assert(bufsize > JAS_STREAM_MAXPUTBACK);
-			stream->bufbase_ = JAS_CAST(uchar *, buf);
+			stream->bufbase_ = JAS_CAST(unsigned char*, buf);
 			stream->bufsize_ = bufsize - JAS_STREAM_MAXPUTBACK;
 		}
 	} else {