@@ -138,7 +138,7 @@ func (cli *DockerCli) hijack(method, path string, setRawTerminal bool, in io.Rea

 	if err != nil {

 		return err

 	}

-	req, err := http.NewRequest(method, fmt.Sprintf("/v%s%s", api.APIVERSION, path), params)

+	req, err := http.NewRequest(method, fmt.Sprintf("/v%s%s", api.Version, path), params)

 	if err != nil {

 		return err

 	}

@@ -53,7 +53,7 @@ func (cli *DockerCli) clientRequest(method, path string, in io.Reader, headers m

 	if expectedPayload && in == nil {

 		in = bytes.NewReader([]byte{})

 	}

-	req, err := http.NewRequest(method, fmt.Sprintf("/v%s%s", api.APIVERSION, path), in)

+	req, err := http.NewRequest(method, fmt.Sprintf("/v%s%s", api.Version, path), in)

 	if err != nil {

 		return nil, nil, -1, err

 	}

@@ -26,7 +26,7 @@ func (cli *DockerCli) CmdVersion(args ...string) error {

 	if dockerversion.VERSION != "" {

 		fmt.Fprintf(cli.out, "Client version: %s\n", dockerversion.VERSION)

 	}

-	fmt.Fprintf(cli.out, "Client API version: %s\n", api.APIVERSION)

+	fmt.Fprintf(cli.out, "Client API version: %s\n", api.Version)

 	fmt.Fprintf(cli.out, "Go version (client): %s\n", runtime.Version())

 	if dockerversion.GITCOMMIT != "" {

 		fmt.Fprintf(cli.out, "Git commit (client): %s\n", dockerversion.GITCOMMIT)

@@ -16,8 +16,14 @@ import (

 // Common constants for daemon and client.

 const (

-	APIVERSION            version.Version = "1.20"       // Current REST API version

-	DefaultDockerfileName string          = "Dockerfile" // Default filename with Docker commands, read by docker build

+	// Current REST API version

+	Version version.Version = "1.20"

+

+	// Minimun REST API version supported

+	MinVersion version.Version = "1.12"

+

+	// Default filename with Docker commands, read by docker build

+	DefaultDockerfileName string = "Dockerfile"

 )

 type ByPrivatePort []types.Port

@@ -244,7 +244,7 @@ func (s *Server) postAuth(version version.Version, w http.ResponseWriter, r *htt

 func (s *Server) getVersion(version version.Version, w http.ResponseWriter, r *http.Request, vars map[string]string) error {

 	v := &types.Version{

 		Version:    dockerversion.VERSION,

-		ApiVersion: api.APIVERSION,

+		ApiVersion: api.Version,

 		GitCommit:  dockerversion.GITCOMMIT,

 		GoVersion:  runtime.Version(),

 		Os:         runtime.GOOS,

@@ -1477,14 +1477,18 @@ func makeHttpHandler(logging bool, localMethod string, localRoute string, handle

 		}

 		version := version.Version(mux.Vars(r)["version"])

 		if version == "" {

-			version = api.APIVERSION

+			version = api.Version

 		}

 		if corsHeaders != "" {

 			writeCorsHeaders(w, r, corsHeaders)

 		}

-		if version.GreaterThan(api.APIVERSION) {

-			http.Error(w, fmt.Errorf("client is newer than server (client API version: %s, server API version: %s)", version, api.APIVERSION).Error(), http.StatusBadRequest)

+		if version.GreaterThan(api.Version) {

+			http.Error(w, fmt.Errorf("client is newer than server (client API version: %s, server API version: %s)", version, api.Version).Error(), http.StatusBadRequest)

+			return

+		}

+		if version.LessThan(api.MinVersion) {

+			http.Error(w, fmt.Errorf("client is too old, minimum supported API version is %s, please upgrade your client to a newer version", api.MinVersion).Error(), http.StatusBadRequest)

 			return

 		}

@@ -3,15 +3,18 @@ package main

 import (

 	"net/http"

 	"net/http/httputil"

+	"strconv"

+	"strings"

 	"time"

+	"github.com/docker/docker/api"

 	"github.com/go-check/check"

 )

 func (s *DockerSuite) TestApiOptionsRoute(c *check.C) {

 	status, _, err := sockRequest("OPTIONS", "/", nil)

-	c.Assert(status, check.Equals, http.StatusOK)

 	c.Assert(err, check.IsNil)

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

 }

 func (s *DockerSuite) TestApiGetEnabledCors(c *check.C) {

@@ -26,7 +29,7 @@ func (s *DockerSuite) TestApiGetEnabledCors(c *check.C) {

 	//c.Assert(res.Header.Get("Access-Control-Allow-Headers"), check.Equals, "Origin, X-Requested-With, Content-Type, Accept, X-Registry-Auth")

 }

-func (s *DockerSuite) TestVersionStatusCode(c *check.C) {

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

 	conn, err := sockConn(time.Duration(10 * time.Second))

 	c.Assert(err, check.IsNil)

@@ -40,3 +43,31 @@ func (s *DockerSuite) TestVersionStatusCode(c *check.C) {

 	res, err := client.Do(req)

 	c.Assert(res.StatusCode, check.Equals, http.StatusBadRequest)

 }

+

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

+	v := strings.Split(string(api.Version), ".")

+	vMinInt, err := strconv.Atoi(v[1])

+	c.Assert(err, check.IsNil)

+	vMinInt++

+	v[1] = strconv.Itoa(vMinInt)

+	version := strings.Join(v, ".")

+

+	status, body, err := sockRequest("GET", "/v"+version+"/version", nil)

+	c.Assert(err, check.IsNil)

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

+	c.Assert(len(string(body)), check.Not(check.Equals), 0) // Expected not empty body

+}

+

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

+	v := strings.Split(string(api.MinVersion), ".")

+	vMinInt, err := strconv.Atoi(v[1])

+	c.Assert(err, check.IsNil)

+	vMinInt--

+	v[1] = strconv.Itoa(vMinInt)

+	version := strings.Join(v, ".")

+

+	status, body, err := sockRequest("GET", "/v"+version+"/version", nil)

+	c.Assert(err, check.IsNil)

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

+	c.Assert(len(string(body)), check.Not(check.Equals), 0) // Expected not empty body

+}