diff --git a/src/pkg/strings/replace.go b/src/pkg/strings/replace.go
index cb9d7b1fa4..d6d742b942 100644
--- a/src/pkg/strings/replace.go
+++ b/src/pkg/strings/replace.go
@@ -6,7 +6,8 @@ package strings
 
 import "io"
 
-// A Replacer replaces a list of strings with replacements.
+// Replacer replaces a list of strings with replacements.
+// It is safe for concurrent use by multiple goroutines.
 type Replacer struct {
 	r replacer
 }