diff --git a/consul/agent/server.go b/consul/agent/server.go
index 6510f34eab..749465224c 100644
--- a/consul/agent/server.go
+++ b/consul/agent/server.go
@@ -86,10 +86,13 @@ func IsConsulServer(m serf.Member) (bool, *Server) {
 		return false, nil
 	}
 
-	raft_vsn_str := m.Tags["raft_vsn"]
-	raft_vsn, err := strconv.Atoi(raft_vsn_str)
-	if err != nil {
-		return false, nil
+	raft_vsn := 0
+	raft_vsn_str, ok := m.Tags["raft_vsn"]
+	if ok {
+		raft_vsn, err = strconv.Atoi(raft_vsn_str)
+		if err != nil {
+			return false, nil
+		}
 	}
 
 	addr := &net.TCPAddr{IP: m.Addr, Port: port}
diff --git a/consul/agent/server_test.go b/consul/agent/server_test.go
index 06321c7e2f..f94c29cb02 100644
--- a/consul/agent/server_test.go
+++ b/consul/agent/server_test.go
@@ -60,6 +60,7 @@ func TestIsConsulServer(t *testing.T) {
 			"dc":       "east-aws",
 			"port":     "10000",
 			"vsn":      "1",
+			"expect":   "3",
 			"raft_vsn": "3",
 		},
 	}
@@ -76,7 +77,7 @@ func TestIsConsulServer(t *testing.T) {
 	if parts.Bootstrap {
 		t.Fatalf("unexpected bootstrap")
 	}
-	if parts.Expect != 0 {
+	if parts.Expect != 3 {
 		t.Fatalf("bad: %v", parts.Expect)
 	}
 	if parts.RaftVersion != 3 {
@@ -114,3 +115,69 @@ func TestIsConsulServer(t *testing.T) {
 		t.Fatalf("unexpected ok server")
 	}
 }
+
+func TestIsConsulServer_Optional(t *testing.T) {
+	m := serf.Member{
+		Name: "foo",
+		Addr: net.IP([]byte{127, 0, 0, 1}),
+		Tags: map[string]string{
+			"role": "consul",
+			"id":   "asdf",
+			"dc":   "east-aws",
+			"port": "10000",
+			"vsn":  "1",
+			// raft_vsn and expect are optional and should default
+			// to zero.
+		},
+	}
+	ok, parts := agent.IsConsulServer(m)
+	if !ok || parts.Datacenter != "east-aws" || parts.Port != 10000 {
+		t.Fatalf("bad: %v %v", ok, parts)
+	}
+	if parts.Name != "foo" {
+		t.Fatalf("bad: %v", parts)
+	}
+	if parts.ID != "asdf" {
+		t.Fatalf("bad: %v", parts.ID)
+	}
+	if parts.Bootstrap {
+		t.Fatalf("unexpected bootstrap")
+	}
+	if parts.Expect != 0 {
+		t.Fatalf("bad: %v", parts.Expect)
+	}
+	if parts.RaftVersion != 0 {
+		t.Fatalf("bad: %v", parts.RaftVersion)
+	}
+	m.Tags["bootstrap"] = "1"
+	m.Tags["disabled"] = "1"
+	ok, parts = agent.IsConsulServer(m)
+	if !ok {
+		t.Fatalf("expected a valid consul server")
+	}
+	if !parts.Bootstrap {
+		t.Fatalf("expected bootstrap")
+	}
+	if parts.Addr.String() != "127.0.0.1:10000" {
+		t.Fatalf("bad addr: %v", parts.Addr)
+	}
+	if parts.Version != 1 {
+		t.Fatalf("bad: %v", parts)
+	}
+	m.Tags["expect"] = "3"
+	delete(m.Tags, "bootstrap")
+	delete(m.Tags, "disabled")
+	ok, parts = agent.IsConsulServer(m)
+	if !ok || parts.Expect != 3 {
+		t.Fatalf("bad: %v", parts.Expect)
+	}
+	if parts.Bootstrap {
+		t.Fatalf("unexpected bootstrap")
+	}
+
+	delete(m.Tags, "role")
+	ok, parts = agent.IsConsulServer(m)
+	if ok {
+		t.Fatalf("unexpected ok server")
+	}
+}