diff --git a/cases/tables.go b/cases/tables.go
index 32ee8fa..e6e95a6 100644
--- a/cases/tables.go
+++ b/cases/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package cases
 
diff --git a/cases/tables_test.go b/cases/tables_test.go
index 7bfc5b3..85ae237 100644
--- a/cases/tables_test.go
+++ b/cases/tables_test.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package cases
 
diff --git a/cases/trieval.go b/cases/trieval.go
index a2edb10..fb221f8 100644
--- a/cases/trieval.go
+++ b/cases/trieval.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package cases
 
diff --git a/collate/tables.go b/collate/tables.go
index 525d852..9ec4f3d 100644
--- a/collate/tables.go
+++ b/collate/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package collate
 
diff --git a/currency/common.go b/currency/common.go
index 0c567f9..250cb8c 100644
--- a/currency/common.go
+++ b/currency/common.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package currency
 
diff --git a/currency/tables.go b/currency/tables.go
index c9a8f4e..a34c7cb 100644
--- a/currency/tables.go
+++ b/currency/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package currency
 
diff --git a/encoding/htmlindex/tables.go b/encoding/htmlindex/tables.go
index 78950d3..cbf4ba9 100644
--- a/encoding/htmlindex/tables.go
+++ b/encoding/htmlindex/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package htmlindex
 
diff --git a/encoding/ianaindex/tables.go b/encoding/ianaindex/tables.go
index 1a04565..98a1d77 100644
--- a/encoding/ianaindex/tables.go
+++ b/encoding/ianaindex/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package ianaindex
 
diff --git a/encoding/internal/identifier/mib.go b/encoding/internal/identifier/mib.go
index 915abfa..768842b 100644
--- a/encoding/internal/identifier/mib.go
+++ b/encoding/internal/identifier/mib.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package identifier
 
diff --git a/gen.go b/gen.go
index cb23273..a694fdd 100644
--- a/gen.go
+++ b/gen.go
@@ -104,8 +104,10 @@
 		cases      = generate("./cases", unicode, norm, language, rangetable)
 		width      = generate("./width", unicode)
 		bidi       = generate("./unicode/bidi", unicode, norm, rangetable)
+		mib        = generate("./encoding/internal/identifier", unicode)
+		_          = generate("./encoding/htmlindex", unicode, language, mib)
+		_          = generate("./encoding/ianaindex", unicode, language, mib)
 		_          = generate("./secure/precis", unicode, norm, rangetable, cases, width, bidi)
-		_          = generate("./encoding/htmlindex", unicode, language)
 		_          = generate("./currency", unicode, cldr, language, internal)
 		_          = generate("./internal/number", unicode, cldr, language, internal)
 		_          = generate("./internal/export/idna", unicode, bidi, norm)
@@ -254,8 +256,13 @@
 		b = bytes.Replace(b, []byte(search), []byte(replace), -1)
 		// Remove go:generate lines.
 		b = goGenRE.ReplaceAllLiteral(b, nil)
-		const comment = "// Copied from the golang.org/x/text repo; DO NOT EDIT\n\n"
-		b = append([]byte(comment), b...)
+		comment := "// Code generated by running \"go generate\" in golang.org/x/text. DO NOT EDIT.\n\n"
+		if *doCore {
+			comment = "// Code generated by running \"go run gen.go -core\" in golang.org/x/text. DO NOT EDIT.\n\n"
+		}
+		if !bytes.HasPrefix(b, []byte(comment)) {
+			b = append([]byte(comment), b...)
+		}
 		if b, err = format.Source(b); err != nil {
 			fmt.Println("Failed to format file:", err)
 			os.Exit(1)
diff --git a/internal/export/idna/common_test.go b/internal/export/idna/common_test.go
index 5f101d7..0b07c12 100644
--- a/internal/export/idna/common_test.go
+++ b/internal/export/idna/common_test.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package idna
 
diff --git a/internal/export/idna/tables.go b/internal/export/idna/tables.go
index 9749d77..d281934 100644
--- a/internal/export/idna/tables.go
+++ b/internal/export/idna/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package idna
 
diff --git a/internal/export/idna/trieval.go b/internal/export/idna/trieval.go
index 2ea5396..63cb03b 100644
--- a/internal/export/idna/trieval.go
+++ b/internal/export/idna/trieval.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package idna
 
diff --git a/internal/gen/gen.go b/internal/gen/gen.go
index 84c699f..2acb035 100644
--- a/internal/gen/gen.go
+++ b/internal/gen/gen.go
@@ -67,7 +67,7 @@
 	flag.Parse()
 }
 
-const header = `// This file was generated by go generate; DO NOT EDIT
+const header = `// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package %s
 
diff --git a/internal/tables.go b/internal/tables.go
index 5e8f5fa..7fb15f6 100644
--- a/internal/tables.go
+++ b/internal/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package internal
 
diff --git a/language/common.go b/language/common.go
index a255bb0..9d86e18 100644
--- a/language/common.go
+++ b/language/common.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package language
 
diff --git a/language/display/tables.go b/language/display/tables.go
index 895b677..0d7ebd7 100644
--- a/language/display/tables.go
+++ b/language/display/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package display
 
diff --git a/language/index.go b/language/index.go
index 50c7521..b370ffa 100644
--- a/language/index.go
+++ b/language/index.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package language
 
diff --git a/language/tables.go b/language/tables.go
index ccdc1ff..a2aec62 100644
--- a/language/tables.go
+++ b/language/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package language
 
diff --git a/search/tables.go b/search/tables.go
index e7f95db..72d27b5 100644
--- a/search/tables.go
+++ b/search/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package search
 
diff --git a/secure/precis/tables.go b/secure/precis/tables.go
index a9b500d..2f550c1 100644
--- a/secure/precis/tables.go
+++ b/secure/precis/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package precis
 
diff --git a/secure/precis/trieval.go b/secure/precis/trieval.go
index fed7d75..4833f96 100644
--- a/secure/precis/trieval.go
+++ b/secure/precis/trieval.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package precis
 
diff --git a/unicode/bidi/ranges_test.go b/unicode/bidi/ranges_test.go
index a1b313e..bfaecd5 100644
--- a/unicode/bidi/ranges_test.go
+++ b/unicode/bidi/ranges_test.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package bidi
 
diff --git a/unicode/bidi/tables.go b/unicode/bidi/tables.go
index 2d4dde0..7212d5a 100644
--- a/unicode/bidi/tables.go
+++ b/unicode/bidi/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package bidi
 
diff --git a/unicode/bidi/trieval.go b/unicode/bidi/trieval.go
index bebd855..4c459c4 100644
--- a/unicode/bidi/trieval.go
+++ b/unicode/bidi/trieval.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package bidi
 
diff --git a/unicode/cldr/xml.go b/unicode/cldr/xml.go
index a1550ed..99fa963 100644
--- a/unicode/cldr/xml.go
+++ b/unicode/cldr/xml.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package cldr
 
diff --git a/unicode/norm/tables.go b/unicode/norm/tables.go
index d1183ff..bf9ff80 100644
--- a/unicode/norm/tables.go
+++ b/unicode/norm/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package norm
 
diff --git a/unicode/rangetable/tables.go b/unicode/rangetable/tables.go
index 25c4dfb..61c989b 100644
--- a/unicode/rangetable/tables.go
+++ b/unicode/rangetable/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package rangetable
 
diff --git a/unicode/runenames/bits.go b/unicode/runenames/bits.go
index 1ec1d82..48cc2c0 100644
--- a/unicode/runenames/bits.go
+++ b/unicode/runenames/bits.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package runenames
 
diff --git a/unicode/runenames/tables.go b/unicode/runenames/tables.go
index 0e9db91..99c4926 100644
--- a/unicode/runenames/tables.go
+++ b/unicode/runenames/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package runenames
 
diff --git a/width/common_test.go b/width/common_test.go
index fb5545e..9ebb782 100644
--- a/width/common_test.go
+++ b/width/common_test.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package width
 
diff --git a/width/runes_test.go b/width/runes_test.go
index 2a48c40..587dab4 100644
--- a/width/runes_test.go
+++ b/width/runes_test.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package width
 
diff --git a/width/tables.go b/width/tables.go
index 242da0f..e21f0b8 100644
--- a/width/tables.go
+++ b/width/tables.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package width
 
diff --git a/width/trieval.go b/width/trieval.go
index 0ecffb4..ca8e45f 100644
--- a/width/trieval.go
+++ b/width/trieval.go
@@ -1,4 +1,4 @@
-// This file was generated by go generate; DO NOT EDIT
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
 package width