diff --git a/src/cmd/go/alldocs.go b/src/cmd/go/alldocs.go
index 051b3daef9..0ea0bad9a9 100644
--- a/src/cmd/go/alldocs.go
+++ b/src/cmd/go/alldocs.go
@@ -525,7 +525,9 @@
 // they are treated as a single package. Within a package, generate processes the
 // source files in a package in file name order, one at a time. Within
 // a source file, generate runs generators in the order they appear
-// in the file, one at a time.
+// in the file, one at a time. The go generate tool also sets the build
+// tag "generate" so that files may be examined by go generate but ignored
+// during build.
 //
 // If any generator returns an error exit status, "go generate" skips
 // all further processing for that package.
diff --git a/src/cmd/go/internal/generate/generate.go b/src/cmd/go/internal/generate/generate.go
index 19597c7a33..f2ae80e5dc 100644
--- a/src/cmd/go/internal/generate/generate.go
+++ b/src/cmd/go/internal/generate/generate.go
@@ -114,7 +114,9 @@ one at a time. If the command line lists .go files from a single directory,
 they are treated as a single package. Within a package, generate processes the
 source files in a package in file name order, one at a time. Within
 a source file, generate runs generators in the order they appear
-in the file, one at a time.
+in the file, one at a time. The go generate tool also sets the build
+tag "generate" so that files may be examined by go generate but ignored
+during build.
 
 If any generator returns an error exit status, "go generate" skips
 all further processing for that package.
@@ -161,6 +163,9 @@ func runGenerate(cmd *base.Command, args []string) {
 			log.Fatalf("generate: %s", err)
 		}
 	}
+
+	cfg.BuildContext.BuildTags = append(cfg.BuildContext.BuildTags, "generate")
+
 	// Even if the arguments are .go files, this loop suffices.
 	printed := false
 	for _, pkg := range load.Packages(args) {
diff --git a/src/internal/syscall/windows/mksyscall.go b/src/internal/syscall/windows/mksyscall.go
index a8edafb3c3..0bf87dc95c 100644
--- a/src/internal/syscall/windows/mksyscall.go
+++ b/src/internal/syscall/windows/mksyscall.go
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build generate
+
 package windows
 
 //go:generate go run $GOROOT/src/syscall/mksyscall_windows.go -output zsyscall_windows.go syscall_windows.go security_windows.go psapi_windows.go symlink_windows.go
diff --git a/src/internal/syscall/windows/registry/mksyscall.go b/src/internal/syscall/windows/registry/mksyscall.go
index 077215351e..fa8e27e8ff 100644
--- a/src/internal/syscall/windows/registry/mksyscall.go
+++ b/src/internal/syscall/windows/registry/mksyscall.go
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build generate
+
 package registry
 
 //go:generate go run $GOROOT/src/syscall/mksyscall_windows.go -output zsyscall_windows.go syscall.go