diff --git a/file_format.md b/file_format.md
index c663473..83ffa9e 100644
--- a/file_format.md
+++ b/file_format.md
@@ -53,11 +53,13 @@ Following the file-count bytes, the following bytes are added for each file:
     1. 2 bytes is 16-bit unsigned integer "link target absolute path" in
        big-endian. This does not include the NULL at the end of the string.
     2. X bytes of link-target-absolute-path (length defined by previous value).
-       Is a NULL-terminated string.
+       Is a NULL-terminated string. If the previous "size" value is 0, then
+       this entry does not exist and should be skipped.
     3. 2 bytes is 16-bit unsigned integer "link target relative path" in
        big-endian. This does not include the NULL at the end of the string.
     4. X bytes of link-target-relative-path (length defined by previous value).
-       Is a NULL-terminated string.
+       Is a NULL-terminated string. If the previous "size" value is 0, then
+       this entry does not exist and should be skipped.
 5. If this file is NOT a symbolic link:
     1. 8 bytes 64-bit unsigned integer "size of filename in this archive file".
     2. X bytes file data (length defined by previous value).