diff --git a/libavcodec/microdvddec.c b/libavcodec/microdvddec.c
index f3c640f932..3780fe28b5 100644
--- a/libavcodec/microdvddec.c
+++ b/libavcodec/microdvddec.c
@@ -148,6 +148,8 @@ static char *microdvd_load_tags(struct microdvd_tag *tags, char *s)
 
         /* Position */
         case 'P':
+            if (!*s)
+                break;
             tag.persistent = MICRODVD_PERSISTENT_ON;
             tag.data1 = (*s++ == '1');
             if (*s != '}')