diff --git a/libavformat/microdvddec.c b/libavformat/microdvddec.c
index 68a5d87ab5..5d5b83fea8 100644
--- a/libavformat/microdvddec.c
+++ b/libavformat/microdvddec.c
@@ -35,7 +35,8 @@ typedef struct {
 
 static int microdvd_probe(AVProbeData *p)
 {
-    unsigned char c, *ptr = p->buf;
+    unsigned char c;
+    const uint8_t *ptr = p->buf;
     int i;
 
     if (AV_RB24(ptr) == 0xEFBBBF)