diff --git a/cmd/bundle/main.go b/cmd/bundle/main.go
index d1f5348e..e4b261fa 100644
--- a/cmd/bundle/main.go
+++ b/cmd/bundle/main.go
@@ -236,7 +236,7 @@ func bundle(src, dst, dstpkg, prefix string) ([]byte, error) {
 
 	var out bytes.Buffer
 
-	fmt.Fprintf(&out, "// Code generated by golang.org/x/tools/cmd/bundle.\n")
+	fmt.Fprintf(&out, "// Code generated by golang.org/x/tools/cmd/bundle. DO NOT EDIT.\n")
 	if *outputFile != "" {
 		fmt.Fprintf(&out, "//go:generate bundle %s\n", strings.Join(os.Args[1:], " "))
 	} else {
diff --git a/cmd/bundle/testdata/out.golden b/cmd/bundle/testdata/out.golden
index 0ca96c9d..9374b2e9 100644
--- a/cmd/bundle/testdata/out.golden
+++ b/cmd/bundle/testdata/out.golden
@@ -1,4 +1,4 @@
-// Code generated by golang.org/x/tools/cmd/bundle.
+// Code generated by golang.org/x/tools/cmd/bundle. DO NOT EDIT.
 //   $ bundle
 
 // The package doc comment
diff --git a/godoc/static/makestatic.go b/godoc/static/makestatic.go
index 9cc69e38..8ee8e556 100644
--- a/godoc/static/makestatic.go
+++ b/godoc/static/makestatic.go
@@ -120,7 +120,7 @@ func sanitize(b []byte) []byte {
 	return bytes.Replace(b, []byte("\xEF\xBB\xBF"), []byte("`+\"\\xEF\\xBB\\xBF\"+`"), -1)
 }
 
-const warning = `// Code generated by "makestatic"; DO NOT EDIT`
+const warning = `// Code generated by "makestatic"; DO NOT EDIT.`
 
 var license = fmt.Sprintf(`// Copyright %d The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/godoc/static/static.go b/godoc/static/static.go
index a4286609..c89ffaad 100644
--- a/godoc/static/static.go
+++ b/godoc/static/static.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Code generated by "makestatic"; DO NOT EDIT
+// Code generated by "makestatic"; DO NOT EDIT.
 
 package static
 
diff --git a/imports/mkstdlib.go b/imports/mkstdlib.go
index 9f626629..5602244a 100644
--- a/imports/mkstdlib.go
+++ b/imports/mkstdlib.go
@@ -40,7 +40,7 @@ func main() {
 	outf := func(format string, args ...interface{}) {
 		fmt.Fprintf(&buf, format, args...)
 	}
-	outf("// AUTO-GENERATED BY mkstdlib.go\n\n")
+	outf("// Code generated by mkstdlib.go. DO NOT EDIT.\n\n")
 	outf("package imports\n")
 	outf("var stdlib = map[string]string{\n")
 	f := io.MultiReader(
diff --git a/imports/zstdlib.go b/imports/zstdlib.go
index b1a2114e..5b66a6cd 100644
--- a/imports/zstdlib.go
+++ b/imports/zstdlib.go
@@ -1,4 +1,4 @@
-// AUTO-GENERATED BY mkstdlib.go
+// Code generated by mkstdlib.go. DO NOT EDIT.
 
 package imports