1 files changed, 8 insertions, 0 deletions
diff --git a/internal/norm/norm.go b/internal/norm/norm.go
index 77bb604..701f765 100644
--- a/internal/norm/norm.go
+++ b/internal/norm/norm.go
@@ -5,6 +5,7 @@
 package norm
 
 import (
+	"fmt"
 	"strings"
 	"unicode"
 
@@ -16,6 +17,13 @@ import (
 // another version are discarded (spec §6.1).
 const Version = 1
 
+// Fingerprint names everything Text and Name's output depends on: Version,
+// and the Unicode tables of the standard library and of x/text's
+// normalisation, which a Go or x/text upgrade can change (review cache F4).
+func Fingerprint() string {
+	return fmt.Sprintf("norm%d unicode%s nfd%s", Version, unicode.Version, unorm.Version)
+}
+
 // special holds the letters that do not decompose under Unicode NFD, so
 // Fold maps them explicitly.
 var special = map[rune]string{