@@ -65,7 +65,7 @@ func (s *Server) postContainerExecStart(version version.Version, w http.Response

 	}

 	var (

 		execName                  = vars["name"]

-		stdin                     io.ReadCloser

+		stdin, inStream           io.ReadCloser

 		stdout, stderr, outStream io.Writer

 	)

@@ -77,7 +77,7 @@ func (s *Server) postContainerExecStart(version version.Version, w http.Response

 	if !execStartCheck.Detach {

 		var err error

 		// Setting up the streaming http interface.

-		inStream, outStream, err := hijackServer(w)

+		inStream, outStream, err = hijackServer(w)

 		if err != nil {

 			return err

 		}

@@ -95,6 +95,8 @@ func (s *Server) postContainerExecStart(version version.Version, w http.Response

 			stderr = stdcopy.NewStdWriter(outStream, stdcopy.Stderr)

 			stdout = stdcopy.NewStdWriter(outStream, stdcopy.Stdout)

 		}

+	} else {

+		outStream = w

 	}

 	// Now run the user process in container.

@@ -595,3 +595,14 @@ func (s *DockerSuite) TestExecOnReadonlyContainer(c *check.C) {

 		c.Fatalf("exec into a read-only container failed with exit status %d", status)

 	}

 }

+

+// #15750

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

+	name := "exec-15750"

+	dockerCmd(c, "run", "-d", "--name", name, "busybox", "top")

+

+	_, errmsg, status := dockerCmdWithStdoutStderr(nil, "exec", name, "no-such-cmd")

+	if status == 255 && !strings.Contains(errmsg, "executable file not found") {

+		c.Fatal("exec error message not received. The daemon might had crashed")

+	}

+}

@@ -602,7 +602,9 @@ func dockerCmdWithError(args ...string) (string, int, error) {

 func dockerCmdWithStdoutStderr(c *check.C, args ...string) (string, string, int) {

 	stdout, stderr, status, err := runCommandWithStdoutStderr(exec.Command(dockerBinary, args...))

-	c.Assert(err, check.IsNil, check.Commentf("%q failed with errors: %s, %v", strings.Join(args, " "), stderr, err))

+	if c != nil {

+		c.Assert(err, check.IsNil, check.Commentf("%q failed with errors: %s, %v", strings.Join(args, " "), stderr, err))

+	}

 	return stdout, stderr, status

 }