diff --git a/devtools/client/responsive.html/index.js b/devtools/client/responsive.html/index.js
index 64a14c021a73..b85c84d1d2db 100644
--- a/devtools/client/responsive.html/index.js
+++ b/devtools/client/responsive.html/index.js
@@ -47,6 +47,7 @@ let bootstrap = {
     });
     let provider = createElement(Provider, { store }, app);
     ReactDOM.render(provider, document.querySelector("#root"));
+    this.initDevices();
     window.postMessage({ type: "init" }, "*");
   },
 
@@ -62,9 +63,28 @@ let bootstrap = {
    * to dispatch.  They can do so here.
    */
   dispatch(action) {
+    if (!this.store) {
+      // If actions are dispatched after store is destroyed, ignore them.  This
+      // can happen in tests that close the tool quickly while async tasks like
+      // initDevices() below are still pending.
+      return;
+    }
     this.store.dispatch(action);
   },
 
+  initDevices() {
+    GetDevices().then(devices => {
+      for (let type of devices.TYPES) {
+        this.dispatch(addDeviceType(type));
+        for (let device of devices[type]) {
+          if (device.os != "fxos") {
+            this.dispatch(addDevice(device, type));
+          }
+        }
+      }
+    });
+  },
+
 };
 
 window.addEventListener("load", function onLoad() {
@@ -92,18 +112,6 @@ Object.defineProperty(window, "store", {
 window.addInitialViewport = contentURI => {
   try {
     bootstrap.dispatch(changeLocation(contentURI));
-
-    GetDevices().then(devices => {
-      for (let type of devices.TYPES) {
-        bootstrap.dispatch(addDeviceType(type));
-        for (let device of devices[type]) {
-          if (device.os != "fxos") {
-            bootstrap.dispatch(addDevice(device, type));
-          }
-        }
-      }
-    });
-
     bootstrap.dispatch(addViewport());
   } catch (e) {
     console.error(e);
diff --git a/devtools/client/responsive.html/test/browser/head.js b/devtools/client/responsive.html/test/browser/head.js
index 246d66a16d00..54680f4505b9 100644
--- a/devtools/client/responsive.html/test/browser/head.js
+++ b/devtools/client/responsive.html/test/browser/head.js
@@ -16,6 +16,8 @@ Services.scriptloader.loadSubScript(
 
 const TEST_URI_ROOT = "http://example.com/browser/devtools/client/responsive.html/test/browser/";
 
+SimpleTest.requestCompleteLog();
+
 DevToolsUtils.testing = true;
 Services.prefs.setCharPref("devtools.devices.url",
   TEST_URI_ROOT + "devices.json");