diff --git a/book/10-git-internals/sections/objects.asc b/book/10-git-internals/sections/objects.asc
index 8f793311c..c502e43c9 100644
--- a/book/10-git-internals/sections/objects.asc
+++ b/book/10-git-internals/sections/objects.asc
@@ -370,7 +370,7 @@ To that first part of the header, Git adds a space followed by the size in bytes
 
 [source,console]
 ----
->> header = "blob #{content.length}\0"
+>> header = "blob #{content.bytesize}\0"
 => "blob 16\u0000"
 ----