diff --git a/src/os/exec.go b/src/os/exec.go
index bc75d4d..2beac55 100644
--- a/src/os/exec.go
+++ b/src/os/exec.go
@@ -149,6 +149,8 @@
 }
 
 // Exited reports whether the program has exited.
+// On Unix systems this reports true if the program exited due to calling exit,
+// but false if the program terminated due to a signal.
 func (p *ProcessState) Exited() bool {
 	return p.exited()
 }