diff --git a/devtools/client/application/test/browser/browser_application_panel_list-domain-workers.js b/devtools/client/application/test/browser/browser_application_panel_list-domain-workers.js
index 932c40bf5ccf..092d49c0b65b 100644
--- a/devtools/client/application/test/browser/browser_application_panel_list-domain-workers.js
+++ b/devtools/client/application/test/browser/browser_application_panel_list-domain-workers.js
@@ -15,6 +15,14 @@ const EMPTY_URL = (URL_ROOT + "resources/service-workers/empty.html").replace(
   "test2.example.com"
 );
 
+// FIXME bug 1575427 this rejection is very common.
+const { PromiseTestUtils } = ChromeUtils.import(
+  "resource://testing-common/PromiseTestUtils.jsm"
+);
+PromiseTestUtils.whitelistRejectionsGlobally(
+  /this._frontCreationListeners is null/
+);
+
 add_task(async function() {
   await enableApplicationPanel();
 
diff --git a/devtools/client/debugger/src/client/firefox/events.js b/devtools/client/debugger/src/client/firefox/events.js
index 2a1185eb5a71..623a4c987c8b 100644
--- a/devtools/client/debugger/src/client/firefox/events.js
+++ b/devtools/client/debugger/src/client/firefox/events.js
@@ -50,14 +50,12 @@ function setupEvents(dependencies: Dependencies) {
   sourceQueue.initialize(actions);
 
   addThreadEventListeners(threadFront);
-  tabTarget.on("workerListChanged", () => threadListChanged("worker"));
-  debuggerClient.mainRoot.on("processListChanged", () =>
-    threadListChanged("contentProcess")
-  );
+  tabTarget.on("workerListChanged", () => threadListChanged());
+  debuggerClient.mainRoot.on("processListChanged", () => threadListChanged());
 
   if (features.windowlessServiceWorkers || attachAllTargets(tabTarget)) {
     const workersListener = new WorkersListener(debuggerClient.mainRoot);
-    workersListener.addListener(() => threadListChanged("worker"));
+    workersListener.addListener(() => threadListChanged());
   }
 }
 
@@ -114,8 +112,8 @@ function newSource(threadFront: ThreadFront, { source }: SourcePacket) {
   });
 }
 
-function threadListChanged(type) {
-  actions.updateThreads(type);
+function threadListChanged() {
+  actions.updateThreads();
 }
 
 function replayFramePositions(
diff --git a/devtools/client/debugger/src/client/firefox/targets.js b/devtools/client/debugger/src/client/firefox/targets.js
index 93632017201c..779456076261 100644
--- a/devtools/client/debugger/src/client/firefox/targets.js
+++ b/devtools/client/debugger/src/client/firefox/targets.js
@@ -90,6 +90,7 @@ async function listWorkerTargets(args: Args) {
   } else {
     workers = (await currentTarget.listWorkers()).workers;
     if (currentTarget.url && features.windowlessServiceWorkers) {
+      allWorkers = await debuggerClient.mainRoot.listAllWorkerTargets();
       const {
         registrations,
       } = await debuggerClient.mainRoot.listServiceWorkerRegistrations();
@@ -100,10 +101,16 @@ async function listWorkerTargets(args: Args) {
   }
 
   for (const front of serviceWorkerRegistrations) {
-    const { activeWorker, waitingWorker, installingWorker } = front;
+    const {
+      activeWorker,
+      waitingWorker,
+      installingWorker,
+      evaluatingWorker,
+    } = front;
     await maybeMarkServiceWorker(activeWorker, "active");
     await maybeMarkServiceWorker(waitingWorker, "waiting");
     await maybeMarkServiceWorker(installingWorker, "installing");
+    await maybeMarkServiceWorker(evaluatingWorker, "evaluating");
   }
 
   async function maybeMarkServiceWorker(info, status) {
@@ -111,9 +118,6 @@ async function listWorkerTargets(args: Args) {
       return;
     }
 
-    if (!allWorkers) {
-      allWorkers = await debuggerClient.mainRoot.listAllWorkerTargets();
-    }
     const worker = allWorkers.find(front => front && front.id == info.id);
     if (!worker) {
       return;
@@ -128,20 +132,37 @@ async function listWorkerTargets(args: Args) {
   return workers;
 }
 
-async function listProcessTargets(args: Args) {
-  const { currentTarget, debuggerClient } = args;
-  if (!attachAllTargets(currentTarget)) {
-    return [];
-  }
-
+async function getAllProcessTargets(args) {
+  const { debuggerClient } = args;
   const { processes } = await debuggerClient.mainRoot.listProcesses();
-  const targets = await Promise.all(
+  return Promise.all(
     processes
       .filter(descriptor => !descriptor.isParent)
       .map(descriptor => descriptor.getTarget())
   );
+}
 
-  return targets;
+async function listProcessTargets(args: Args) {
+  const { currentTarget } = args;
+  if (!attachAllTargets(currentTarget)) {
+    if (currentTarget.url && features.windowlessServiceWorkers) {
+      // Service workers associated with our target's origin need to pause until
+      // we attach, regardless of which process they are running in.
+      const origin = new URL(currentTarget.url).origin;
+      const targets = await getAllProcessTargets(args);
+      try {
+        await Promise.all(
+          targets.map(t => t.pauseMatchingServiceWorkers({ origin }))
+        );
+      } catch (e) {
+        // Old servers without pauseMatchingServiceWorkers will throw.
+        // @backward-compatibility: remove in Firefox 75
+      }
+    }
+    return [];
+  }
+
+  return getAllProcessTargets(args);
 }
 
 export async function updateTargets(args: Args) {
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg-windowless-service-workers.js b/devtools/client/debugger/test/mochitest/browser_dbg-windowless-service-workers.js
index ce7f743f75a2..ae6989445d94 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg-windowless-service-workers.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg-windowless-service-workers.js
@@ -7,6 +7,14 @@ async function checkWorkerThreads(dbg, count) {
   ok(true, `Have ${count} threads`);
 }
 
+async function checkWorkerStatus(dbg, status) {
+  await waitUntil(() => {
+    const threads = dbg.selectors.getThreads();
+    return threads.some(t => t.serviceWorkerStatus == status);
+  });
+  ok(true, `Have thread with status ${status}`);
+}
+
 // Test that we can detect a new service worker and hit breakpoints that we've
 // set in it.
 add_task(async function() {
@@ -31,8 +39,9 @@ add_task(async function() {
   await waitForPaused(dbg);
   assertPausedAtSourceAndLine(dbg, workerSource.id, 13);
 
-  // Leave the breakpoint in place for the next subtest.
+  // Leave the breakpoint and worker in place for the next subtest.
   await resume(dbg);
+  await waitForRequestsToSettle(dbg);
   await removeTab(gBrowser.selectedTab);
 });
 
@@ -61,6 +70,7 @@ add_task(async function() {
   invokeInTab("unregisterWorker");
 
   await checkWorkerThreads(dbg, 0);
+  await waitForRequestsToSettle(dbg);
   await removeTab(gBrowser.selectedTab);
 });
 
@@ -73,6 +83,7 @@ add_task(async function() {
 
   invokeInTab("registerWorker");
   await checkWorkerThreads(dbg, 1);
+  await checkWorkerStatus(dbg, "active");
 
   const firstTab = gBrowser.selectedTab;
 
@@ -101,9 +112,13 @@ add_task(async function() {
   ok(content0.value.includes("newServiceWorker") != content1.value.includes("newServiceWorker"),
      "Got two different sources for service worker");
 
+  // Add a breakpoint for the next subtest.
+  await addBreakpoint(dbg, "service-worker.sjs", 2);
+
   invokeInTab("unregisterWorker");
 
   await checkWorkerThreads(dbg, 0);
+  await waitForRequestsToSettle(dbg);
   await removeTab(firstTab);
   await removeTab(secondTab);
 
@@ -111,3 +126,41 @@ add_task(async function() {
   await addTab(EXAMPLE_URL + "service-worker.sjs?setStatus=");
   await removeTab(gBrowser.selectedTab);
 });
+
+// Test setting breakpoints while the service worker is starting up.
+add_task(async function() {
+  info("Subtest #4");
+
+  const toolbox = await openNewTabAndToolbox(EXAMPLE_URL + "doc-service-workers.html", "jsdebugger");
+  const dbg = createDebuggerContext(toolbox);
+
+  invokeInTab("registerWorker");
+  await checkWorkerThreads(dbg, 1);
+
+  await waitForSource(dbg, "service-worker.sjs");
+  const workerSource = findSource(dbg, "service-worker.sjs");
+
+  await waitForBreakpointCount(dbg, 1);
+  await waitForPaused(dbg);
+  assertPausedAtSourceAndLine(dbg, workerSource.id, 2);
+  await checkWorkerStatus(dbg, "evaluating");
+
+  await addBreakpoint(dbg, "service-worker.sjs", 19);
+  await resume(dbg);
+  await waitForPaused(dbg);
+  assertPausedAtSourceAndLine(dbg, workerSource.id, 19);
+  await checkWorkerStatus(dbg, "installing");
+
+  await addBreakpoint(dbg, "service-worker.sjs", 5);
+  await resume(dbg);
+  await waitForPaused(dbg);
+  assertPausedAtSourceAndLine(dbg, workerSource.id, 5);
+  await checkWorkerStatus(dbg, "active");
+
+  await resume(dbg);
+  invokeInTab("unregisterWorker");
+
+  await checkWorkerThreads(dbg, 0);
+  await waitForRequestsToSettle(dbg);
+  await removeTab(gBrowser.selectedTab);
+});
diff --git a/devtools/client/debugger/test/mochitest/examples/service-worker.sjs b/devtools/client/debugger/test/mochitest/examples/service-worker.sjs
index 8d4d3d2aa06e..b48bb9e9076a 100644
--- a/devtools/client/debugger/test/mochitest/examples/service-worker.sjs
+++ b/devtools/client/debugger/test/mochitest/examples/service-worker.sjs
@@ -19,6 +19,10 @@ self.addEventListener("fetch", event => {
     event.respondWith(response);
   }
 });
+
+self.addEventListener("install", event => {
+  dump("Install\\n");
+});
 `;
 
 function handleRequest(request, response) {
@@ -30,17 +34,5 @@ function handleRequest(request, response) {
   }
 
   const status = getState("status");
-
-  let newBody = body.replace("STATUS", status);
-
-  if (status == "stuckInstall") {
-newBody += `
-self.addEventListener("install", event => {
-  dump("Install\\n");
-  event.waitUntil(new Promise(resolve => {}));
-});
-`;
-  }
-
-  response.write(newBody);
+  response.write(body.replace("STATUS", status));
 }