diff --git a/src/go/build/doc.go b/src/go/build/doc.go
index 75a827bb91f..78e17b220a0 100644
--- a/src/go/build/doc.go
+++ b/src/go/build/doc.go
@@ -111,7 +111,7 @@
 // (example: source_windows_amd64.go) where GOOS and GOARCH represent
 // any known operating system and architecture values respectively, then
 // the file is considered to have an implicit build constraint requiring
-// those terms.
+// those terms (in addition to any explicit constraints in the file).
 //
 // To keep a file from being considered for the build:
 //