README.md in unicode-age-1.1.0 vs README.md in unicode-age-2.0.0.pre

@@ -12,10 +12,12 @@
 Unicode::Age.of "🛒" # => 9.0
 Unicode::Age.of "\u{10FFFF}" # => nil
 Unicode::Age.of "\u{10FFFD}" # => 2.0
 ```
 
-Characters of status "Unassigned" (Unicode General Category of **Cn**) will return `nil`.
+Characters of status "Unassigned" (Unicode General Category of **Cn**) will raise a `Unicode::Age::UnknownAge` exception.
+
+**This is a breaking change:** In the current non-*pre* version of the gem on rubygems.org, unassigned characters will just return `nil`
 
 ## Supported Ruby/Unicode versions
 
 Ruby version | Unicode version
 -------------|----------------