@@ -298,7 +298,13 @@ func (s *Server) postContainersKill(version version.Version, w http.ResponseWrit

 	}

 	if err := s.daemon.ContainerKill(name, sig); err != nil {

-		return err

+		_, isStopped := err.(daemon.ErrContainerNotRunning)

+		// Return error that's not caused because the container is stopped.

+		// Return error if the container is not running and the api is >= 1.20

+		// to keep backwards compatibility.

+		if version.GreaterThanOrEqualTo("1.20") || !isStopped {

+			return fmt.Errorf("Cannot kill container %s: %v", name, err)

+		}

 	}

 	w.WriteHeader(http.StatusNoContent)

@@ -41,6 +41,14 @@ var (

 	ErrContainerRootfsReadonly = errors.New("container rootfs is marked read-only")

 )

+type ErrContainerNotRunning struct {

+	id string

+}

+

+func (e ErrContainerNotRunning) Error() string {

+	return fmt.Sprintf("Container %s is not running", e.id)

+}

+

 type StreamConfig struct {

 	stdout    *broadcastwriter.BroadcastWriter

 	stderr    *broadcastwriter.BroadcastWriter

@@ -361,7 +369,7 @@ func (container *Container) KillSig(sig int) error {

 	}

 	if !container.Running {

-		return fmt.Errorf("Container %s is not running", container.ID)

+		return ErrContainerNotRunning{container.ID}

 	}

 	// signal to the monitor that it should not restart the container

@@ -398,7 +406,7 @@ func (container *Container) Pause() error {

 	// We cannot Pause the container which is not running

 	if !container.Running {

-		return fmt.Errorf("Container %s is not running, cannot pause a non-running container", container.ID)

+		return ErrContainerNotRunning{container.ID}

 	}

 	// We cannot Pause the container which is already paused

@@ -420,7 +428,7 @@ func (container *Container) Unpause() error {

 	// We cannot unpause the container which is not running

 	if !container.Running {

-		return fmt.Errorf("Container %s is not running, cannot unpause a non-running container", container.ID)

+		return ErrContainerNotRunning{container.ID}

 	}

 	// We cannot unpause the container which is not paused

@@ -438,7 +446,7 @@ func (container *Container) Unpause() error {

 func (container *Container) Kill() error {

 	if !container.IsRunning() {

-		return fmt.Errorf("Container %s is not running", container.ID)

+		return ErrContainerNotRunning{container.ID}

 	}

 	// 1. Send SIGKILL

@@ -520,7 +528,7 @@ func (container *Container) Restart(seconds int) error {

 func (container *Container) Resize(h, w int) error {

 	if !container.IsRunning() {

-		return fmt.Errorf("Cannot resize container %s, container is not running", container.ID)

+		return ErrContainerNotRunning{container.ID}

 	}

 	if err := container.command.ProcessConfig.Terminal.Resize(h, w); err != nil {

 		return err

@@ -1,9 +1,6 @@

 package daemon

-import (

-	"fmt"

-	"syscall"

-)

+import "syscall"

 // ContainerKill send signal to the container

 // If no signal is given (sig 0), then Kill with SIGKILL and wait

@@ -18,12 +15,12 @@ func (daemon *Daemon) ContainerKill(name string, sig uint64) error {

 	// If no signal is passed, or SIGKILL, perform regular Kill (SIGKILL + wait())

 	if sig == 0 || syscall.Signal(sig) == syscall.SIGKILL {

 		if err := container.Kill(); err != nil {

-			return fmt.Errorf("Cannot kill container %s: %s", name, err)

+			return err

 		}

 	} else {

 		// Otherwise, just send the requested signal

 		if err := container.KillSig(int(sig)); err != nil {

-			return fmt.Errorf("Cannot kill container %s: %s", name, err)

+			return err

 		}

 	}

 	return nil

@@ -1,6 +1,8 @@

 package main

 import (

+	"fmt"

+	"net/http"

 	"strings"

 	"github.com/go-check/check"

@@ -87,3 +89,12 @@ func (s *DockerSuite) TestKillWithInvalidSignal(c *check.C) {

 		c.Fatal("Container should be in running state after an invalid signal")

 	}

 }

+

+func (s *DockerSuite) TestKillofStoppedContainerAPIPre120(c *check.C) {

+	dockerCmd(c, "run", "--name", "docker-kill-test-api", "-d", "busybox", "top")

+	dockerCmd(c, "stop", "docker-kill-test-api")

+

+	status, _, err := sockRequest("POST", fmt.Sprintf("/v1.19/containers/%s/kill", "docker-kill-test-api"), nil)

+	c.Assert(err, check.IsNil)

+	c.Assert(status, check.Equals, http.StatusNoContent)

+}