diff --git a/command/agent/local.go b/command/agent/local.go
index e456ebb2e5..ea1217f827 100644
--- a/command/agent/local.go
+++ b/command/agent/local.go
@@ -434,11 +434,26 @@ func (l *localState) setSyncState() error {
 		if l.config.CheckUpdateInterval == 0 {
 			equal = existing.IsSame(check)
 		} else {
-			eCopy := new(structs.HealthCheck)
-			*eCopy = *existing
-			eCopy.Output = ""
-			check.Output = ""
-			equal = eCopy.IsSame(check)
+			// Copy the existing check before potentially modifying
+			// it before the compare operation.
+			eCopy := existing.Clone()
+
+			// Copy the server's check before modifying, otherwise
+			// in-memory RPC-based unit tests will have side effects.
+			cCopy := check.Clone()
+
+			// If there's a defer timer active then we've got a
+			// potentially spammy check so we don't sync the output
+			// during this sweep since the timer will mark the check
+			// out of sync for us. Otherwise, it is safe to sync the
+			// output now. This is especially important for checks
+			// that don't change state after they are created, in
+			// which case we'd never see their output synced back ever.
+			if _, ok := l.deferCheck[id]; ok {
+				eCopy.Output = ""
+				cCopy.Output = ""
+			}
+			equal = eCopy.IsSame(cCopy)
 		}
 
 		// Update the status
@@ -499,6 +514,8 @@ func (l *localState) syncChanges() error {
 		if err := l.syncNodeInfo(); err != nil {
 			return err
 		}
+	} else {
+		l.logger.Printf("[DEBUG] agent: Node info in sync")
 	}
 
 	return nil
diff --git a/command/agent/local_test.go b/command/agent/local_test.go
index 62c418f819..0b4e880fb3 100644
--- a/command/agent/local_test.go
+++ b/command/agent/local_test.go
@@ -654,7 +654,7 @@ func TestAgentAntiEntropy_Checks(t *testing.T) {
 
 func TestAgentAntiEntropy_Check_DeferSync(t *testing.T) {
 	conf := nextConfig()
-	conf.CheckUpdateInterval = 100 * time.Millisecond
+	conf.CheckUpdateInterval = 500 * time.Millisecond
 	dir, agent := makeAgent(t, conf)
 	defer os.RemoveAll(dir)
 	defer agent.Shutdown()
@@ -693,8 +693,8 @@ func TestAgentAntiEntropy_Check_DeferSync(t *testing.T) {
 	// Update the check output! Should be deferred
 	agent.state.UpdateCheck("web", structs.HealthPassing, "output")
 
-	// Should not update for 100 milliseconds
-	time.Sleep(50 * time.Millisecond)
+	// Should not update for 500 milliseconds
+	time.Sleep(250 * time.Millisecond)
 	if err := agent.RPC("Health.NodeChecks", &req, &checks); err != nil {
 		t.Fatalf("err: %v", err)
 	}
@@ -729,6 +729,112 @@ func TestAgentAntiEntropy_Check_DeferSync(t *testing.T) {
 	}, func(err error) {
 		t.Fatalf("err: %s", err)
 	})
+
+	// Change the output in the catalog to force it out of sync.
+	eCopy := check.Clone()
+	eCopy.Output = "changed"
+	reg := structs.RegisterRequest{
+		Datacenter:      agent.config.Datacenter,
+		Node:            agent.config.NodeName,
+		Address:         agent.config.AdvertiseAddr,
+		TaggedAddresses: agent.config.TaggedAddresses,
+		Check:           eCopy,
+		WriteRequest:    structs.WriteRequest{},
+	}
+	var out struct{}
+	if err := agent.RPC("Catalog.Register", &reg, &out); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	// Verify that the output is out of sync.
+	if err := agent.RPC("Health.NodeChecks", &req, &checks); err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	for _, chk := range checks.HealthChecks {
+		switch chk.CheckID {
+		case "web":
+			if chk.Output != "changed" {
+				t.Fatalf("unexpected update: %v", chk)
+			}
+		}
+	}
+
+	// Trigger anti-entropy run and wait.
+	agent.StartSync()
+	time.Sleep(200 * time.Millisecond)
+
+	// Verify that the output was synced back to the agent's value.
+	if err := agent.RPC("Health.NodeChecks", &req, &checks); err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	for _, chk := range checks.HealthChecks {
+		switch chk.CheckID {
+		case "web":
+			if chk.Output != "output" {
+				t.Fatalf("missed update: %v", chk)
+			}
+		}
+	}
+
+	// Reset the catalog again.
+	if err := agent.RPC("Catalog.Register", &reg, &out); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	// Verify that the output is out of sync.
+	if err := agent.RPC("Health.NodeChecks", &req, &checks); err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	for _, chk := range checks.HealthChecks {
+		switch chk.CheckID {
+		case "web":
+			if chk.Output != "changed" {
+				t.Fatalf("unexpected update: %v", chk)
+			}
+		}
+	}
+
+	// Now make an update that should be deferred.
+	agent.state.UpdateCheck("web", structs.HealthPassing, "deferred")
+
+	// Trigger anti-entropy run and wait.
+	agent.StartSync()
+	time.Sleep(200 * time.Millisecond)
+
+	// Verify that the output is still out of sync since there's a deferred
+	// update pending.
+	if err := agent.RPC("Health.NodeChecks", &req, &checks); err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	for _, chk := range checks.HealthChecks {
+		switch chk.CheckID {
+		case "web":
+			if chk.Output != "changed" {
+				t.Fatalf("unexpected update: %v", chk)
+			}
+		}
+	}
+
+	// Wait for the deferred update.
+	testutil.WaitForResult(func() (bool, error) {
+		if err := agent.RPC("Health.NodeChecks", &req, &checks); err != nil {
+			return false, err
+		}
+
+		// Verify updated
+		for _, chk := range checks.HealthChecks {
+			switch chk.CheckID {
+			case "web":
+				if chk.Output != "deferred" {
+					return false, fmt.Errorf("no update: %v", chk)
+				}
+			}
+		}
+
+		return true, nil
+	}, func(err error) {
+		t.Fatalf("err: %s", err)
+	})
 }
 
 func TestAgentAntiEntropy_NodeInfo(t *testing.T) {
diff --git a/consul/structs/structs.go b/consul/structs/structs.go
index d582560cd8..1979b9b9ee 100644
--- a/consul/structs/structs.go
+++ b/consul/structs/structs.go
@@ -396,6 +396,13 @@ func (c *HealthCheck) IsSame(other *HealthCheck) bool {
 	return true
 }
 
+// Clone returns a distinct clone of the HealthCheck.
+func (c *HealthCheck) Clone() *HealthCheck {
+	clone := new(HealthCheck)
+	*clone = *c
+	return clone
+}
+
 type HealthChecks []*HealthCheck
 
 // CheckServiceNode is used to provide the node, its service
diff --git a/consul/structs/structs_test.go b/consul/structs/structs_test.go
index 6a71116888..d7672cad57 100644
--- a/consul/structs/structs_test.go
+++ b/consul/structs/structs_test.go
@@ -211,6 +211,28 @@ func TestStructs_HealthCheck_IsSame(t *testing.T) {
 	check(&other.ServiceName)
 }
 
+func TestStructs_HealthCheck_Clone(t *testing.T) {
+	hc := &HealthCheck{
+		Node:        "node1",
+		CheckID:     "check1",
+		Name:        "thecheck",
+		Status:      HealthPassing,
+		Notes:       "it's all good",
+		Output:      "lgtm",
+		ServiceID:   "service1",
+		ServiceName: "theservice",
+	}
+	clone := hc.Clone()
+	if !hc.IsSame(clone) {
+		t.Fatalf("should be equal to its clone")
+	}
+
+	clone.Output = "different"
+	if hc.IsSame(clone) {
+		t.Fatalf("should not longer be equal to its clone")
+	}
+}
+
 func TestStructs_CheckServiceNodes_Shuffle(t *testing.T) {
 	// Make a huge list of nodes.
 	var nodes CheckServiceNodes