diff --git a/cmd/godoc/x.go b/cmd/godoc/x.go
index 31934b43..41b38ad3 100644
--- a/cmd/godoc/x.go
+++ b/cmd/godoc/x.go
@@ -26,6 +26,7 @@ var xMap = map[string]xRepo{
 
 	"benchmarks": {"https://go.googlesource.com/benchmarks", "git"},
 	"blog":       {"https://go.googlesource.com/blog", "git"},
+	"build":      {"https://go.googlesource.com/build", "git"},
 	"crypto":     {"https://go.googlesource.com/crypto", "git"},
 	"debug":      {"https://go.googlesource.com/debug", "git"},
 	"exp":        {"https://go.googlesource.com/exp", "git"},