md-text-float does not work with ng-disabled, version 0.5.1

[ghost]

Markup:

<md-text-float fid="fedTaxId" name="fedTaxId" label="Federal Tax ID" 
  ng-model="revenue.service.data.revenue.fedTaxId"
  ng-disabled="registrant.service.isRegistrantInputDisabled()" type="text" required>
</md-text-float>

Generated:

<md-input-group ng-disabled="registrant.service.isRegistrantInputDisabled() isDisabled" 
  tabindex="-1" fid="fedTaxId" name="fedTaxId" label="Federal Tax ID" 
  ng-model="revenue.service.data.revenue.fedTaxId" 
  class="ng-isolate-scope md-default-theme ng-invalid ng-invalid-required" 
  aria-required="true" aria-invalid="true"> 
  <label for="fedTaxId" class="ng-binding">Federal Tax ID</label> 
  <input id="fedTaxId" ng-model="value" type="text" tabindex="0" aria-disabled="false" 
    aria-invalid="false" class="ng-valid">
</md-input-group>

Error:

Error: [$parse:syntax] Syntax Error: Token 'isDisabled' is an unexpected token at column 48 of the expression [registrant.service.isRegistrantInputDisabled() isDisabled] starting at [isDisabled].
http://errors.angularjs.org/1.3.1/$parse/syntax?p0=isDisabled&p1=is%20an%20unexpected%20token&p2=48&p3=registrant.service.isRegistrantInputDisabled()NaNsDisabled&p4=isDisabled
    at http://localhost:8080/bower_components/angular/angular.js:80:12
    at Parser.throwError (http://localhost:8080/bower_components/angular/angular.js:11808:11)
    at Parser.parse (http://localhost:8080/bower_components/angular/angular.js:11759:12)
    at $parse (http://localhost:8080/bower_components/angular/angular.js:12398:39)
    at Scope.$watch (http://localhost:8080/bower_components/angular/angular.js:13544:19)
    at http://localhost:8080/bower_components/angular-aria/angular-aria.js:100:15
    at invokeLinkFn (http://localhost:8080/bower_components/angular/angular.js:8081:9)
    at nodeLinkFn (http://localhost:8080/bower_components/angular/angular.js:7593:11)
    at compositeLinkFn (http://localhost:8080/bower_components/angular/angular.js:6959:13)
    at nodeLinkFn (http://localhost:8080/bower_components/angular/angular.js:7588:24)