diff --git a/libavformat/file.c b/libavformat/file.c
index 0e3577d070..3cfd28c2a4 100644
--- a/libavformat/file.c
+++ b/libavformat/file.c
@@ -36,21 +36,26 @@
 
 /* standard file protocol */
 
+typedef struct FileContext {
+    int fd;
+} FileContext;
+
 static int file_read(URLContext *h, unsigned char *buf, int size)
 {
-    int fd = (intptr_t) h->priv_data;
-    return read(fd, buf, size);
+    FileContext *c = h->priv_data;
+    return read(c->fd, buf, size);
 }
 
 static int file_write(URLContext *h, const unsigned char *buf, int size)
 {
-    int fd = (intptr_t) h->priv_data;
-    return write(fd, buf, size);
+    FileContext *c = h->priv_data;
+    return write(c->fd, buf, size);
 }
 
 static int file_get_handle(URLContext *h)
 {
-    return (intptr_t) h->priv_data;
+    FileContext *c = h->priv_data;
+    return c->fd;
 }
 
 static int file_check(URLContext *h, int mask)
@@ -70,6 +75,7 @@ static int file_check(URLContext *h, int mask)
 
 static int file_open(URLContext *h, const char *filename, int flags)
 {
+    FileContext *c = h->priv_data;
     int access;
     int fd;
 
@@ -88,26 +94,26 @@ static int file_open(URLContext *h, const char *filename, int flags)
     fd = open(filename, access, 0666);
     if (fd == -1)
         return AVERROR(errno);
-    h->priv_data = (void *) (intptr_t) fd;
+    c->fd = fd;
     return 0;
 }
 
 /* XXX: use llseek */
 static int64_t file_seek(URLContext *h, int64_t pos, int whence)
 {
-    int fd = (intptr_t) h->priv_data;
+    FileContext *c = h->priv_data;
     if (whence == AVSEEK_SIZE) {
         struct stat st;
-        int ret = fstat(fd, &st);
+        int ret = fstat(c->fd, &st);
         return ret < 0 ? AVERROR(errno) : st.st_size;
     }
-    return lseek(fd, pos, whence);
+    return lseek(c->fd, pos, whence);
 }
 
 static int file_close(URLContext *h)
 {
-    int fd = (intptr_t) h->priv_data;
-    return close(fd);
+    FileContext *c = h->priv_data;
+    return close(c->fd);
 }
 
 URLProtocol ff_file_protocol = {
@@ -119,6 +125,7 @@ URLProtocol ff_file_protocol = {
     .url_close           = file_close,
     .url_get_file_handle = file_get_handle,
     .url_check           = file_check,
+    .priv_data_size      = sizeof(FileContext),
 };
 
 #endif /* CONFIG_FILE_PROTOCOL */
@@ -127,6 +134,7 @@ URLProtocol ff_file_protocol = {
 
 static int pipe_open(URLContext *h, const char *filename, int flags)
 {
+    FileContext *c = h->priv_data;
     int fd;
     char *final;
     av_strstart(filename, "pipe:", &filename);
@@ -142,7 +150,7 @@ static int pipe_open(URLContext *h, const char *filename, int flags)
 #if HAVE_SETMODE
     setmode(fd, O_BINARY);
 #endif
-    h->priv_data = (void *) (intptr_t) fd;
+    c->fd = fd;
     h->is_streamed = 1;
     return 0;
 }
@@ -154,6 +162,7 @@ URLProtocol ff_pipe_protocol = {
     .url_write           = file_write,
     .url_get_file_handle = file_get_handle,
     .url_check           = file_check,
+    .priv_data_size      = sizeof(FileContext),
 };
 
 #endif /* CONFIG_PIPE_PROTOCOL */