--- a/devtools/client/jsonview/test/head.js
+++ b/devtools/client/jsonview/test/head.js
@@ -22,43 +22,38 @@ registerCleanupFunction(() => {
 
 // XXX move some API into devtools/framework/test/shared-head.js
 
 /**
  * Add a new test tab in the browser and load the given url.
  * @param {String} url The url to be loaded in the new tab
  * @return a promise that resolves to the tab object when the url is loaded
  */
-function addJsonViewTab(url) {
+async function addJsonViewTab(url) {
   info("Adding a new JSON tab with URL: '" + url + "'");
 
-  let deferred = promise.defer();
-  addTab(url).then(tab => {
-    let browser = tab.linkedBrowser;
+  const tab = await addTab(url);
+  let browser = tab.linkedBrowser;
 
-    // Load devtools/shared/frame-script-utils.js
-    getFrameScript();
-
-    // Load frame script with helpers for JSON View tests.
-    let rootDir = getRootDirectory(gTestPath);
-    let frameScriptUrl = rootDir + "doc_frame_script.js";
-    browser.messageManager.loadFrameScript(frameScriptUrl, false);
+  // Load devtools/shared/frame-script-utils.js
+  getFrameScript();
 
-    // Resolve if the JSONView is fully loaded or wait
-    // for an initialization event.
-    if (content.window.wrappedJSObject.jsonViewInitialized) {
-      deferred.resolve(tab);
-    } else {
-      waitForContentMessage("Test:JsonView:JSONViewInitialized").then(() => {
-        deferred.resolve(tab);
-      });
-    }
-  });
+  // Load frame script with helpers for JSON View tests.
+  let rootDir = getRootDirectory(gTestPath);
+  let frameScriptUrl = rootDir + "doc_frame_script.js";
+  browser.messageManager.loadFrameScript(frameScriptUrl, false);
 
-  return deferred.promise;
+  // Resolve if the JSONView is fully loaded or wait
+  // for an initialization event.
+  if (content.window.wrappedJSObject.jsonViewInitialized) {
+    return tab;
+  }
+
+  await waitForContentMessage("Test:JsonView:JSONViewInitialized");
+  return tab;
 }
 
 /**
  * Expanding a node in the JSON tree
  */
 function clickJsonNode(selector) {
   info("Expanding node: '" + selector + "'");
 
@@ -126,19 +121,19 @@ function sendString(str, selector) {
     selector: selector,
     str: str
   };
 
   return executeInContent("Test:JsonView:SendString", data);
 }
 
 function waitForTime(delay) {
-  let deferred = promise.defer();
-  setTimeout(deferred.resolve, delay);
-  return deferred.promise;
+  return new Promise((resolve, reject) => {
+    setTimeout(resolve, delay);
+  });
 }
 
 function waitForFilter() {
   return executeInContent("Test:JsonView:WaitForFilter");
 }
 
 function normalizeNewLines(value) {
   return value.replace("(\r\n|\n)", "\n");