diff --git a/src/pkg/os/file.go b/src/pkg/os/file.go
index dff8fa862c..0e97e0bd93 100644
--- a/src/pkg/os/file.go
+++ b/src/pkg/os/file.go
@@ -4,6 +4,8 @@
 
 // Package os provides a platform-independent interface to operating system
 // functionality.  The design is Unix-like.
+// The os interface is intended to be uniform across all operating systems.
+// Features not generally available appear in the system-specific package syscall.
 package os
 
 import (