diff --git a/libavformat/mpjpegdec.c b/libavformat/mpjpegdec.c
index 49fe6f650e..2507bb0738 100644
--- a/libavformat/mpjpegdec.c
+++ b/libavformat/mpjpegdec.c
@@ -250,8 +250,8 @@ static int parse_multipart_header(AVIOContext *pb,
 static char* mpjpeg_get_boundary(AVIOContext* pb)
 {
     uint8_t *mime_type = NULL;
-    uint8_t *start;
-    uint8_t *end;
+    const char *start;
+    const char *end;
     uint8_t *res = NULL;
     int     len;