--- a/devtools/client/netmonitor/components/monitor-panel.js
+++ b/devtools/client/netmonitor/components/monitor-panel.js
@@ -8,16 +8,17 @@ const {
   createClass,
   createFactory,
   DOM,
   PropTypes,
 } = require("devtools/client/shared/vendor/react");
 const { connect } = require("devtools/client/shared/vendor/react-redux");
 const { findDOMNode } = require("devtools/client/shared/vendor/react-dom");
 const Actions = require("../actions/index");
+const { getLongString } = require("../utils/client");
 const { Prefs } = require("../utils/prefs");
 const { getFormDataSections } = require("../utils/request-utils");
 const { getSelectedRequest } = require("../selectors/index");
 
 // Components
 const SplitBox = createFactory(require("devtools/client/shared/components/splitter/split-box"));
 const NetworkDetailsPanel = createFactory(require("../shared/components/network-details-panel"));
 const RequestList = createFactory(require("./request-list"));
@@ -64,16 +65,17 @@ const MonitorPanel = createClass({
     } = request;
 
     if (!formDataSections && requestHeaders &&
         requestHeadersFromUploadStream && requestPostData) {
       getFormDataSections(
         requestHeaders,
         requestHeadersFromUploadStream,
         requestPostData,
+        getLongString,
       ).then((newFormDataSections) => {
         updateRequest(
           request.id,
           { formDataSections: newFormDataSections },
           true,
         );
       });
     }

--- a/devtools/client/netmonitor/netmonitor-controller.js
+++ b/devtools/client/netmonitor/netmonitor-controller.js
@@ -510,28 +510,28 @@ NetworkEventsHandler.prototype = {
       responseHeaders,
       requestCookies,
       requestHeaders,
       requestPostData,
     } = action.data;
     let request = getRequestById(gStore.getState(), action.id);
 
     if (requestHeaders && requestHeaders.headers && requestHeaders.headers.length) {
-      let headers = await fetchHeaders(requestHeaders);
+      let headers = await fetchHeaders(requestHeaders, getLongString);
       if (headers) {
         await gStore.dispatch(Actions.updateRequest(
           action.id,
           { requestHeaders: headers },
           true,
         ));
       }
     }
 
     if (responseHeaders && responseHeaders.headers && responseHeaders.headers.length) {
-      let headers = await fetchHeaders(responseHeaders);
+      let headers = await fetchHeaders(responseHeaders, getLongString);
       if (headers) {
         await gStore.dispatch(Actions.updateRequest(
           action.id,
           { responseHeaders: headers },
           true,
         ));
       }
     }

--- a/devtools/client/netmonitor/request-list-context-menu.js
+++ b/devtools/client/netmonitor/request-list-context-menu.js
@@ -217,17 +217,18 @@ RequestListContextMenu.prototype = {
    */
   async copyPostData() {
     let selected = this.selectedRequest;
 
     // Try to extract any form data parameters.
     let formDataSections = await getFormDataSections(
       selected.requestHeaders,
       selected.requestHeadersFromUploadStream,
-      selected.requestPostData);
+      selected.requestPostData,
+      getLongString);
 
     let params = [];
     formDataSections.forEach(section => {
       let paramsArray = parseQueryString(section);
       if (paramsArray) {
         params = [...params, ...paramsArray];
       }
     });

--- a/devtools/client/netmonitor/utils/request-utils.js
+++ b/devtools/client/netmonitor/utils/request-utils.js
@@ -1,28 +1,26 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 /* eslint-disable mozilla/reject-some-requires */
 
 "use strict";
 
-const { getLongString } = require("./client");
-
 /**
  * Extracts any urlencoded form data sections (e.g. "?foo=bar&baz=42") from a
  * POST request.
  *
  * @param {object} headers - the "requestHeaders".
  * @param {object} uploadHeaders - the "requestHeadersFromUploadStream".
  * @param {object} postData - the "requestPostData".
  * @return {array} a promise list that is resolved with the extracted form data.
  */
-async function getFormDataSections(headers, uploadHeaders, postData) {
+async function getFormDataSections(headers, uploadHeaders, postData, getLongString) {
   let formDataSections = [];
 
   let requestHeaders = headers.headers;
   let payloadHeaders = uploadHeaders ? uploadHeaders.headers : [];
   let allHeaders = [...payloadHeaders, ...requestHeaders];
 
   let contentTypeHeader = allHeaders.find(e => {
     return e.name.toLowerCase() == "content-type";
@@ -49,17 +47,17 @@ async function getFormDataSections(heade
 }
 
 /**
  * Fetch headers full content from actor server
  *
  * @param {object} headers - a object presents headers data
  * @return {object} a headers object with updated content payload
  */
-async function fetchHeaders(headers) {
+async function fetchHeaders(headers, getLongString) {
   for (let { value } of headers.headers) {
     headers.headers.value = await getLongString(value);
   }
   return headers;
 }
 
 /**
  * Form a data: URI given a mime type, encoding, and some text.