diff --git a/libavcodec/bitstream.h b/libavcodec/bitstream.h
index 62b8bc9f6c..e1ec934b28 100644
--- a/libavcodec/bitstream.h
+++ b/libavcodec/bitstream.h
@@ -85,6 +85,7 @@ typedef struct PutBitContext {
     int bit_left;
     uint8_t *buf, *buf_ptr, *buf_end;
 #endif
+    int size_in_bits;
 } PutBitContext;
 
 static inline void init_put_bits(PutBitContext *s, uint8_t *buffer, int buffer_size)
@@ -94,6 +95,7 @@ static inline void init_put_bits(PutBitContext *s, uint8_t *buffer, int buffer_s
         buffer = NULL;
     }
 
+    s->size_in_bits= 8*buffer_size;
     s->buf = buffer;
     s->buf_end = s->buf + buffer_size;
 #ifdef ALT_BITSTREAM_WRITER