diff --git a/etcd_test.go b/etcd_test.go
index cb43a2a4f..786c6a745 100644
--- a/etcd_test.go
+++ b/etcd_test.go
@@ -6,6 +6,8 @@ import (
 	"github.com/coreos/go-etcd/etcd"
 	"math/rand"
 	"net/http"
+	"net/http/httptest"
+	"net/url"
 	"os"
 	"strconv"
 	"strings"
@@ -54,6 +56,53 @@ func TestSingleNode(t *testing.T) {
 	}
 }
 
+// TestInternalVersionFail will ensure that etcd does not come up if the internal raft
+// versions do not match.
+func TestInternalVersionFail(t *testing.T) {
+	checkedVersion := false
+	testMux := http.NewServeMux()
+
+	testMux.HandleFunc("/version", func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprintln(w, "This is not a version number")
+		checkedVersion = true
+	})
+
+	testMux.HandleFunc("/join", func(w http.ResponseWriter, r *http.Request) {
+		t.Fatal("should not attempt to join!")
+	})
+
+	ts := httptest.NewServer(testMux)
+	defer ts.Close()
+
+	fakeURL, _ := url.Parse(ts.URL)
+
+	procAttr := new(os.ProcAttr)
+	procAttr.Files = []*os.File{nil, os.Stdout, os.Stderr}
+	args := []string{"etcd", "-n=node1", "-f", "-d=/tmp/node1", "-vv", "-C="+fakeURL.Host}
+
+	process, err := os.StartProcess("etcd", args, procAttr)
+	if err != nil {
+		t.Fatal("start process failed:" + err.Error())
+		return
+	}
+	defer process.Kill()
+
+	time.Sleep(time.Second)
+
+	_, err = http.Get("http://127.0.0.1:4001")
+
+	if err == nil {
+		t.Fatal("etcd node should not be up")
+		return
+	}
+
+	if checkedVersion == false {
+		t.Fatal("etcd did not check the version")
+		return
+	}
+}
+
+
 // This test creates a single node and then set a value to it.
 // Then this test kills the node and restart it and tries to get the value again.
 func TestSingleNodeRecovery(t *testing.T) {
diff --git a/raft_server.go b/raft_server.go
index ec4a3feff..800da0152 100644
--- a/raft_server.go
+++ b/raft_server.go
@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"crypto/tls"
 	"encoding/json"
+	"io/ioutil"
 	"fmt"
 	etcdErr "github.com/coreos/etcd/error"
 	"github.com/coreos/go-raft"
@@ -163,15 +164,41 @@ func (r *raftServer) startTransport(scheme string, tlsConf tls.Config) {
 
 }
 
+func getLeaderVersion(t transporter, versionURL url.URL) (string, error) {
+	resp, err := t.Get(versionURL.String())
+
+	if err != nil {
+		return "", err
+	}
+
+	defer resp.Body.Close()
+	body, err := ioutil.ReadAll(resp.Body)
+
+	return string(body), nil
+}
+
 // Send join requests to the leader.
 func joinCluster(s *raft.Server, raftURL string, scheme string) error {
 	var b bytes.Buffer
 
-	json.NewEncoder(&b).Encode(newJoinCommand())
-
 	// t must be ok
 	t, _ := r.Transporter().(transporter)
 
+	// Our version must match the leaders version
+	versionURL := url.URL{Host: raftURL, Scheme: scheme, Path: "/version"}
+	version, err := getLeaderVersion(t, versionURL)
+	if err != nil {
+		return fmt.Errorf("Unable to join: %v", err)
+	}
+
+	// TODO: versioning of the internal protocol. See:
+	// Documentation/internatl-protocol-versioning.md
+	if version != r.version {
+		return fmt.Errorf("Unable to join: internal version mismatch, entire cluster must be running identical versions of etcd")
+	}
+
+	json.NewEncoder(&b).Encode(newJoinCommand())
+
 	joinURL := url.URL{Host: raftURL, Scheme: scheme, Path: "/join"}
 
 	debugf("Send Join Request to %s", raftURL)