diff --git a/libavformat/avio.c b/libavformat/avio.c
index 326bb0aa78..4896782072 100644
--- a/libavformat/avio.c
+++ b/libavformat/avio.c
@@ -349,7 +349,9 @@ int ffurl_write(URLContext *h, const unsigned char *buf, int size)
     if (h->max_packet_size && size > h->max_packet_size)
         return AVERROR(EIO);
 
-    return retry_transfer_wrapper(h, (unsigned char *)buf, size, size, (void*)h->prot->url_write);
+    return retry_transfer_wrapper(h, (unsigned char *)buf, size, size,
+                                  (int (*)(struct URLContext *, uint8_t *, int))
+                                  h->prot->url_write);
 }
 
 int64_t ffurl_seek(URLContext *h, int64_t pos, int whence)
diff --git a/libavformat/aviobuf.c b/libavformat/aviobuf.c
index 537c11f6b4..7de59f10f3 100644
--- a/libavformat/aviobuf.c
+++ b/libavformat/aviobuf.c
@@ -778,7 +778,9 @@ int ffio_fdopen(AVIOContext **s, URLContext *h)
         return AVERROR(ENOMEM);
 
     *s = avio_alloc_context(buffer, buffer_size, h->flags & AVIO_FLAG_WRITE, h,
-                            (void*)ffurl_read, (void*)ffurl_write, (void*)ffurl_seek);
+                            (int (*)(void *, uint8_t *, int)) ffurl_read,
+                            (int (*)(void *, uint8_t *, int)) ffurl_write,
+                            (int64_t (*)(void *, int64_t, int)) ffurl_seek);
     if (!*s) {
         av_free(buffer);
         return AVERROR(ENOMEM);