diff --git a/pep-0440.txt b/pep-0440.txt
index 7215cd476..6739c4491 100644
--- a/pep-0440.txt
+++ b/pep-0440.txt
@@ -61,7 +61,8 @@ run the software.
 Public version identifiers
 --------------------------
 
-Public version identifiers MUST comply with the following scheme::
+The canonical public version identifiers MUST comply with the following
+scheme::
 
     [N!]N(.N)*[{a|b|c}N][.postN][.devN]
 
@@ -70,8 +71,9 @@ Public version identifiers MUST NOT include leading or trailing whitespace.
 Public version identifiers MUST be unique within a given distribution.
 
 Installation tools SHOULD ignore any public versions which do not comply with
-this scheme. Installation tools MAY warn the user when non-compliant
-or ambiguous versions are detected.
+this scheme but MUST also include the normalizations specified below.
+Installation tools MAY warn the user when non-compliant or ambiguous versions
+are detected.
 
 Public version identifiers are separated into up to five segments: