diff --git a/src/os/file.go b/src/os/file.go
index 74d3c9f9631..e546441497b 100644
--- a/src/os/file.go
+++ b/src/os/file.go
@@ -46,6 +46,10 @@ func (f *File) Name() string { return f.name }
 
 // Stdin, Stdout, and Stderr are open Files pointing to the standard input,
 // standard output, and standard error file descriptors.
+//
+// Note that the Go runtime writes to standard error for panics and crashes;
+// closing Stderr may cause those messages to go elsewhere, perhaps
+// to a file opened later.
 var (
 	Stdin  = NewFile(uintptr(syscall.Stdin), "/dev/stdin")
 	Stdout = NewFile(uintptr(syscall.Stdout), "/dev/stdout")