diff --git a/src/pkg/os/exec_unix.go b/src/pkg/os/exec_unix.go
index 7fe7c2f..a5c2281 100644
--- a/src/pkg/os/exec_unix.go
+++ b/src/pkg/os/exec_unix.go
@@ -29,7 +29,7 @@
 // (WNOHANG etc.) affect the behavior of the Wait call.
 func (p *Process) Wait(options int) (w *Waitmsg, err error) {
 	if p.Pid == -1 {
-		return nil, EINVAL
+		return nil, syscall.EINVAL
 	}
 	var status syscall.WaitStatus
 	var rusage *syscall.Rusage