title: Azure Functions Proxy - unable to set a HTTP header if value contains JSON
body: <p>I am trying to set <code>Report-To</code> HTTP header with a proxy function, but the proxy doesn't even start when the value of the header contains a JSON value.</p>
  
  <pre><code>{
      "$schema": "http://json.schemastore.org/proxies",
      "proxies": {
          "proxy1": {
              "debug": true,
              "matchCondition": {
                  "methods": [ "GET" ],
                  "route": "/{*all}"
              },
              "backendUri": "https://*****.z6.web.core.windows.net/{all}",
              "responseOverrides": {
                  "response.headers.Reply-To": "{{ \"TEST\":0 }}"
              }
          }
      }
  }
  </code></pre>
  
  <p>This function returns HTTP error 503 Service unavailable "Functionhost is not running." if I try it on Azure. If started locally, the runtime show the following error message:</p>
  
  <pre><code>[26. 11. 2018 21:29:45] A ScriptHost error has occurred
  [26. 11. 2018 21:29:45] Microsoft.Azure.AppService.Proxy.Common: ; expected
  [26. 11. 2018 21:29:45] ; expected
  [26. 11. 2018 21:29:45] The name 'TEST' does not exist in the current context
  [26. 11. 2018 21:29:45] Only assignment, call, increment, decrement, and new object expressions can be used as a statement.
  [26. 11. 2018 21:29:45] Stopping Host
  </code></pre>
  
  <p>Is something wrong with my proxy definition or is it a bug in Azure Functions?</p>