diff --git a/command/agent/agent.go b/command/agent/agent.go
index 417c4552e..14db1ea3d 100644
--- a/command/agent/agent.go
+++ b/command/agent/agent.go
@@ -549,22 +549,6 @@ func (a *Agent) WANMembers() []serf.Member {
 	}
 }
 
-// CanServersUnderstandProtocol checks to see if all the servers understand the
-// given protocol version.
-func (a *Agent) CanServersUnderstandProtocol(version uint8) bool {
-	numServers, numWhoGrok := 0, 0
-	members := a.LANMembers()
-	for _, member := range members {
-		if member.Tags["role"] == "consul" {
-			numServers++
-			if member.ProtocolMax >= version {
-				numWhoGrok++
-			}
-		}
-	}
-	return (numServers > 0) && (numWhoGrok == numServers)
-}
-
 // StartSync is called once Services and Checks are registered.
 // This is called to prevent a race between clients and the anti-entropy routines
 func (a *Agent) StartSync() {
@@ -603,13 +587,19 @@ func (a *Agent) sendCoordinate() {
 
 		select {
 		case <-time.After(intv):
-			if !a.CanServersUnderstandProtocol(3) {
+			members := a.LANMembers()
+			grok, err := consul.CanServersUnderstandProtocol(members, 3)
+			if err != nil {
+				a.logger.Printf("[ERR] agent: failed to check servers: %s", err)
+				continue
+			}
+			if !grok {
+				a.logger.Printf("[DEBUG] agent: skipping coordinate updates until servers are upgraded")
 				continue
 			}
 
-			var c *coordinate.Coordinate
-			var err error
-			if c, err = a.GetCoordinate(); err != nil {
+			c, err := a.GetCoordinate()
+			if err != nil {
 				a.logger.Printf("[ERR] agent: failed to get coordinate: %s", err)
 				continue
 			}
diff --git a/command/agent/agent_test.go b/command/agent/agent_test.go
index cf1f6c0b6..24fad74af 100644
--- a/command/agent/agent_test.go
+++ b/command/agent/agent_test.go
@@ -1602,30 +1602,3 @@ func TestAgent_GetCoordinate(t *testing.T) {
 	check(true)
 	check(false)
 }
-
-func TestAgent_CanServersUnderstandProtocol(t *testing.T) {
-	config := nextConfig()
-	dir, agent := makeAgent(t, config)
-	defer os.RemoveAll(dir)
-	defer agent.Shutdown()
-
-	min := uint8(consul.ProtocolVersionMin)
-	if !agent.CanServersUnderstandProtocol(min) {
-		t.Fatalf("should grok %d", min)
-	}
-
-	max := uint8(consul.ProtocolVersionMax)
-	if !agent.CanServersUnderstandProtocol(max) {
-		t.Fatalf("should grok %d", max)
-	}
-
-	current := uint8(config.Protocol)
-	if !agent.CanServersUnderstandProtocol(current) {
-		t.Fatalf("should grok %d", current)
-	}
-
-	future := max + 1
-	if agent.CanServersUnderstandProtocol(future) {
-		t.Fatalf("should not grok %d", future)
-	}
-}
diff --git a/consul/coordinate_endpoint.go b/consul/coordinate_endpoint.go
index 4f429bead..db156df5d 100644
--- a/consul/coordinate_endpoint.go
+++ b/consul/coordinate_endpoint.go
@@ -87,8 +87,12 @@ func (c *Coordinate) batchApplyUpdates() error {
 			end = size
 		}
 
+		// We set the "safe to ignore" flag on this update type so old
+		// servers don't crash if they see one of these.
+		t := structs.CoordinateBatchUpdateType | structs.IgnoreUnknownTypeFlag
+
 		slice := updates[start:end]
-		if _, err := c.srv.raftApply(structs.CoordinateBatchUpdateType, slice); err != nil {
+		if _, err := c.srv.raftApply(t, slice); err != nil {
 			return err
 		}
 	}
diff --git a/consul/util.go b/consul/util.go
index f5a29a49b..8dd51c091 100644
--- a/consul/util.go
+++ b/consul/util.go
@@ -95,6 +95,35 @@ func ensurePath(path string, dir bool) error {
 	return os.MkdirAll(path, 0755)
 }
 
+// CanServersUnderstandProtocol checks to see if all the servers in the given
+// list understand the given protocol version. If there are no servers in the
+// list then this will return false.
+func CanServersUnderstandProtocol(members []serf.Member, version uint8) (bool, error) {
+	numServers, numWhoGrok := 0, 0
+	for _, m := range members {
+		if m.Tags["role"] != "consul" {
+			continue
+		}
+		numServers++
+
+		vsn_min, err := strconv.Atoi(m.Tags["vsn_min"])
+		if err != nil {
+			return false, err
+		}
+
+		vsn_max, err := strconv.Atoi(m.Tags["vsn_max"])
+		if err != nil {
+			return false, err
+		}
+
+		v := int(version)
+		if (v >= vsn_min) && (v <= vsn_max) {
+			numWhoGrok++
+		}
+	}
+	return (numServers > 0) && (numWhoGrok == numServers), nil
+}
+
 // Returns if a member is a consul server. Returns a bool,
 // the datacenter, and the rpc port
 func isConsulServer(m serf.Member) (bool, *serverParts) {
diff --git a/consul/util_test.go b/consul/util_test.go
index d2f08c397..88a2c0393 100644
--- a/consul/util_test.go
+++ b/consul/util_test.go
@@ -2,6 +2,7 @@ package consul
 
 import (
 	"errors"
+	"fmt"
 	"net"
 	"regexp"
 	"testing"
@@ -118,6 +119,103 @@ func TestIsPrivateIP(t *testing.T) {
 	}
 }
 
+func TestUtil_CanServersUnderstandProtocol(t *testing.T) {
+	var members []serf.Member
+
+	// All empty list cases should return false.
+	for v := ProtocolVersionMin; v <= ProtocolVersionMax; v++ {
+		grok, err := CanServersUnderstandProtocol(members, v)
+		if err != nil {
+			t.Fatalf("err: %v", err)
+		}
+		if grok {
+			t.Fatalf("empty list should always return false")
+		}
+	}
+
+	// Add a non-server member.
+	members = append(members, serf.Member{
+		Tags: map[string]string{
+			"vsn_min": fmt.Sprintf("%d", ProtocolVersionMin),
+			"vsn_max": fmt.Sprintf("%d", ProtocolVersionMax),
+		},
+	})
+
+	// Make sure it doesn't get counted.
+	for v := ProtocolVersionMin; v <= ProtocolVersionMax; v++ {
+		grok, err := CanServersUnderstandProtocol(members, v)
+		if err != nil {
+			t.Fatalf("err: %v", err)
+		}
+		if grok {
+			t.Fatalf("non-server members should not be counted")
+		}
+	}
+
+	// Add a server member.
+	members = append(members, serf.Member{
+		Tags: map[string]string{
+			"role":    "consul",
+			"vsn_min": fmt.Sprintf("%d", ProtocolVersionMin),
+			"vsn_max": fmt.Sprintf("%d", ProtocolVersionMax),
+		},
+	})
+
+	// Now it should report that it understands.
+	for v := ProtocolVersionMin; v <= ProtocolVersionMax; v++ {
+		grok, err := CanServersUnderstandProtocol(members, v)
+		if err != nil {
+			t.Fatalf("err: %v", err)
+		}
+		if !grok {
+			t.Fatalf("server should grok")
+		}
+	}
+
+	// Nobody should understand anything from the future.
+	for v := uint8(ProtocolVersionMax + 1); v <= uint8(ProtocolVersionMax+10); v++ {
+		grok, err := CanServersUnderstandProtocol(members, v)
+		if err != nil {
+			t.Fatalf("err: %v", err)
+		}
+		if grok {
+			t.Fatalf("server should not grok")
+		}
+	}
+
+	// Add an older server.
+	members = append(members, serf.Member{
+		Tags: map[string]string{
+			"role":    "consul",
+			"vsn_min": fmt.Sprintf("%d", ProtocolVersionMin),
+			"vsn_max": fmt.Sprintf("%d", ProtocolVersionMax-1),
+		},
+	})
+
+	// The servers should no longer understand the max version.
+	for v := ProtocolVersionMin; v <= ProtocolVersionMax; v++ {
+		grok, err := CanServersUnderstandProtocol(members, v)
+		if err != nil {
+			t.Fatalf("err: %v", err)
+		}
+		expected := v < ProtocolVersionMax
+		if grok != expected {
+			t.Fatalf("bad: %v != %v", grok, expected)
+		}
+	}
+
+	// Try a version that's too low for the minimum.
+	{
+		grok, err := CanServersUnderstandProtocol(members, 0)
+		if err != nil {
+			t.Fatalf("err: %v", err)
+		}
+		if grok {
+			t.Fatalf("server should not grok")
+		}
+	}
+}
+
 func TestIsConsulServer(t *testing.T) {
 	m := serf.Member{
 		Name: "foo",