diff --git a/src/os/user/lookup.go b/src/os/user/lookup.go
index 2243a25788..b36b7c01c0 100644
--- a/src/os/user/lookup.go
+++ b/src/os/user/lookup.go
@@ -7,6 +7,10 @@ package user
 import "sync"
 
 // Current returns the current user.
+//
+// The first call will cache the current user information.
+// Subsequent calls will return the cached value and will not reflect
+// changes to the current user.
 func Current() (*User, error) {
 	cache.Do(func() { cache.u, cache.err = current() })
 	if cache.err != nil {