diff --git a/libav/avformat.h b/libav/avformat.h
index e17c7a514b0308e8b8ce311e8cab4b25116332c3..10de1f8c2c91761fea742df51438a63e789c5584 100644
--- a/libav/avformat.h
+++ b/libav/avformat.h
@@ -178,6 +178,8 @@ AVFormat *guess_format(const char *short_name, const char *filename, const char
 
 int strstart(const char *str, const char *val, const char **ptr);
 void nstrcpy(char *buf, int buf_size, const char *str);
+/* This does what strncpy ought to do. */
+void strlcpy(char *dst, const char *src, int dst_size);
 int match_ext(const char *filename, const char *extensions);
 
 void register_all(void);