diff --git a/libavformat/avio.h b/libavformat/avio.h
index 109d20a4ff..bb9b4574f7 100644
--- a/libavformat/avio.h
+++ b/libavformat/avio.h
@@ -71,7 +71,7 @@ typedef struct {
     void *opaque;
     int (*read_packet)(void *opaque, uint8_t *buf, int buf_size);
     int (*write_packet)(void *opaque, uint8_t *buf, int buf_size);
-    int (*seek)(void *opaque, offset_t offset, int whence);
+    offset_t (*seek)(void *opaque, offset_t offset, int whence);
     offset_t pos; /* position in the file of the current buffer */
     int must_flush; /* true if the next seek should flush */
     int eof_reached; /* true if eof reached */
@@ -91,7 +91,7 @@ int init_put_byte(ByteIOContext *s,
                   void *opaque,
                   int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
                   int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
-                  int (*seek)(void *opaque, offset_t offset, int whence));
+                  offset_t (*seek)(void *opaque, offset_t offset, int whence));
 
 void put_byte(ByteIOContext *s, int b);
 void put_buffer(ByteIOContext *s, const unsigned char *buf, int size);
diff --git a/libavformat/aviobuf.c b/libavformat/aviobuf.c
index 993ba449f0..06da44d8dc 100644
--- a/libavformat/aviobuf.c
+++ b/libavformat/aviobuf.c
@@ -29,7 +29,7 @@ int init_put_byte(ByteIOContext *s,
                   void *opaque,
                   int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
                   int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
-                  int (*seek)(void *opaque, offset_t offset, int whence))
+                  offset_t (*seek)(void *opaque, offset_t offset, int whence))
 {
     s->buffer = buffer;
     s->buffer_size = buffer_size;
@@ -491,7 +491,7 @@ static int url_read_packet(void *opaque, uint8_t *buf, int buf_size)
     return url_read(h, buf, buf_size);
 }
 
-static int url_seek_packet(void *opaque, int64_t offset, int whence)
+static offset_t url_seek_packet(void *opaque, offset_t offset, int whence)
 {
     URLContext *h = opaque;
     return url_seek(h, offset, whence);
@@ -701,7 +701,7 @@ static int dyn_packet_buf_write(void *opaque, uint8_t *buf, int buf_size)
     return dyn_buf_write(opaque, buf, buf_size);
 }
 
-static int dyn_buf_seek(void *opaque, offset_t offset, int whence)
+static offset_t dyn_buf_seek(void *opaque, offset_t offset, int whence)
 {
     DynBuffer *d = opaque;