diff --git a/libavformat/subtitles.c b/libavformat/subtitles.c
index fce2bf190b..b7795d8104 100644
--- a/libavformat/subtitles.c
+++ b/libavformat/subtitles.c
@@ -24,7 +24,7 @@
 #include "libavutil/avstring.h"
 
 AVPacket *ff_subtitles_queue_insert(FFDemuxSubtitlesQueue *q,
-                                    const uint8_t *event, int len, int merge)
+                                    const uint8_t *event, size_t len, int merge)
 {
     AVPacket *subs, *sub;
 
@@ -218,7 +218,7 @@ int ff_smil_extract_next_chunk(AVIOContext *pb, AVBPrint *buf, char *c)
 const char *ff_smil_get_attr_ptr(const char *s, const char *attr)
 {
     int in_quotes = 0;
-    const int len = strlen(attr);
+    const size_t len = strlen(attr);
 
     while (*s) {
         while (*s) {
diff --git a/libavformat/subtitles.h b/libavformat/subtitles.h
index b5a96ec08c..5ed23d0fb9 100644
--- a/libavformat/subtitles.h
+++ b/libavformat/subtitles.h
@@ -47,7 +47,7 @@ typedef struct {
  *              previous one instead of adding a new entry, 0 otherwise
  */
 AVPacket *ff_subtitles_queue_insert(FFDemuxSubtitlesQueue *q,
-                                    const uint8_t *event, int len, int merge);
+                                    const uint8_t *event, size_t len, int merge);
 
 /**
  * Set missing durations and sort subtitles by PTS, and then byte position.