diff --git a/ch05.asciidoc b/ch05.asciidoc
index 9186e5fd..a85a59a5 100644
--- a/ch05.asciidoc
+++ b/ch05.asciidoc
@@ -164,7 +164,7 @@ BIP-39 defines the creation of a mnemonic code and seed, which we describe here
 Mnemonic words are generated automatically by the wallet, using a standardized process defined in BIP-39. The wallet starts from a source of entropy, adds a checksum and then maps the entropy to a word list:
 
 1. Create a random sequence (entropy) of 128 to 256 bits.
-2. Create a checksum of the random sequence by taking the first four bits of its SHA256 hash.
+2. Create a checksum of the random sequence by taking the first (entropy-length / 32) bits of its SHA256 hash.
 3. Add the checksum to the end of the random sequence.
 4. Divide the sequence into sections of 11 bits.
 5. Map each 11-bit value to a word from the predefined dictionary of 2048 words.