diff --git a/pkg/kn/commands/service/service_update.go b/pkg/kn/commands/service/service_update.go
index 88eeb27669..e10000ec65 100644
--- a/pkg/kn/commands/service/service_update.go
+++ b/pkg/kn/commands/service/service_update.go
@@ -16,6 +16,7 @@ package service
 
 import (
 	"errors"
+	"fmt"
 
 	"github.com/knative/client/pkg/kn/commands"
 	"github.com/spf13/cobra"
@@ -26,7 +27,7 @@ func NewServiceUpdateCommand(p *commands.KnParams) *cobra.Command {
 	var editFlags ConfigurationEditFlags
 
 	serviceUpdateCommand := &cobra.Command{
-		Use:   "update NAME",
+		Use:   "update NAME [flags]",
 		Short: "Update a service.",
 		Example: `
   # Updates a service 'mysvc' with new environment variables
@@ -39,6 +40,10 @@ func NewServiceUpdateCommand(p *commands.KnParams) *cobra.Command {
 				return errors.New("requires the service name.")
 			}
 
+			if cmd.Flags().NFlag() == 0 {
+				return fmt.Errorf("Flag(s) not set\nUsage: %s", cmd.Use)
+			}
+
 			namespace, err := commands.GetNamespace(cmd)
 			if err != nil {
 				return err
diff --git a/pkg/kn/commands/service/service_update_test.go b/pkg/kn/commands/service/service_update_test.go
index fc1cd87d5e..0f1bb72747 100644
--- a/pkg/kn/commands/service/service_update_test.go
+++ b/pkg/kn/commands/service/service_update_test.go
@@ -18,6 +18,7 @@ import (
 	"errors"
 	"fmt"
 	"reflect"
+	"strings"
 	"testing"
 
 	"github.com/knative/client/pkg/kn/commands"
@@ -63,6 +64,26 @@ func fakeServiceUpdate(original *v1alpha1.Service, args []string) (
 	return
 }
 
+func TestServcieUpdateNoFlags(t *testing.T) {
+	orig := newEmptyService()
+
+	action, _, _, err := fakeServiceUpdate(orig, []string{
+		"service", "update", "foo"})
+
+	if action != nil {
+		t.Errorf("Unexpected action if no flag(s) set")
+	}
+
+	if err != nil {
+		expectedErrMsg := "Flag(s) not set"
+		if !strings.Contains(err.Error(), expectedErrMsg) {
+			t.Errorf("Missing %s in %s", expectedErrMsg, err.Error())
+		}
+	} else {
+		t.Errorf("Error is expected if no flag(s) set")
+	}
+}
+
 func TestServiceUpdateImage(t *testing.T) {
 	orig := newEmptyService()