@@ -228,6 +228,13 @@ func (c *Cluster) Update(version uint64, spec types.Spec, flags types.UpdateFlag

 			return err

 		}

+		// Validate spec name.

+		if spec.Annotations.Name == "" {

+			spec.Annotations.Name = "default"

+		} else if spec.Annotations.Name != "default" {

+			return validationError{errors.New(`swarm spec must be named "default"`)}

+		}

+

 		// In update, client should provide the complete spec of the swarm, including

 		// Name and Labels. If a field is specified with 0 or nil, then the default value

 		// will be used to swarmkit.