diff --git a/libcontainer/container_linux.go b/libcontainer/container_linux.go
index ae5d4fb46b4..d7f0c450781 100644
--- a/libcontainer/container_linux.go
+++ b/libcontainer/container_linux.go
@@ -371,6 +371,11 @@ func (c *Container) Signal(s os.Signal) error {
 	// To avoid a PID reuse attack, don't kill non-running container.
 	switch status {
 	case Running, Created, Paused:
+	case Stopped:
+		// if PID namespace is shared, we should send signal to other processes.
+		if !c.cgroupManager.Exists() {
+			return nil
+		}
 	default:
 		return ErrNotRunning
 	}