title: CloudFormation: Template error: every Ref object must have a single String value
body: <p>I'm attempting to create a CloudFormation stack and am getting the following error:</p>
  <blockquote>
  <p>A client error (ValidationError) occurred when calling the CreateStack operation: Template error: every Ref object must have a single String value.</p>
  </blockquote>
  <p>However, when I grep the template looking for <code>Ref</code> objects they are all Strings except for a single lookup which looks like</p>
  <pre class="lang-json prettyprint-override"><code>{
    &quot;Ref&quot;: {
       &quot;Fn::FindInMap&quot;: [
           &quot;InfraMap&quot;,
           &quot;SecurityGroups&quot;,
           &quot;NATSecurityGroup&quot;
       ]
    }
  }
  </code></pre>
  <p>The value for this reference is <code>&quot;NATSecurityGroup&quot;: &quot;sg-54e6be30&quot;,</code> which seems OK to me.</p>
  <p>Any other thoughts on what this error could be referring to?</p>